I have been driving a fiesta 1.6 diesel (company car) for 8 months now and although quite happy with it I am a tad annoyed by the fuel consumption. The technical spec mentions that anything up to nearly 70 to the gallone can be achieved and indeed it must have impressed someone enough to let it off with 35 quid road tax. The reality is that nothing like 70mpg is attainable or 60 or even 50. The cars computer gives an average of just 42 mpg. I thought it might be a problem with the computer itself so I filled up, noted the mileage and set off from Milton Keynes to Bristol and back and a fair bit of running round MK. Filling up again showed that I had achieved 44 mpg which I recon is pretty poor bearing in mind Fords claim. I generally keep within the speed limit, don't accelerate like a nutter and don't run around with a bag of cement in the boot so what's going wrong here?
If I had bought the car with my own money could I take it back to Ford demanding my money back because there's no way this vehicle will achieve anything like the fuel consumption they claim?
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You don't have to be a speeder to have a driving style that guzzles fuel, poor gear selection lugging the engine (whilst going slowly) or poor anticipation meaning you're always on the brakes or accelerator can mean increased fuel consumption - of course the car may have a slight fault! My brothers C5 has the same engine and he regularly sees 55+ mpg despite the little engine pulling a big car.
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Ours does 53mpg average just local running about & 60 + on a run. If we use supermarket diesel it drops to 47 & I can garantee that everytime but many on the forum argue that supermarket fuel is identical to all the others.
We keep the revs down low & don't go over 2200 rpm on a run to get nearer 70.
If you use the turbo to gain some pulling powere you will use more fuel
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If I had bought the car with my own money could I take it back to Ford demanding my money back because there's no way this vehicle will achieve anything like the fuel consumption they claim?
It's not really Ford's claim - they use an an EU standard test. The cars are engineered to well in the test, hence the low tax.
Someone in Germany did just sue Mercedes and won damages though, and his car was only 9% worse. Maybe that trend will spread.
Yours is way out though. I don't hold with this "check your tyre pressures, it the way you drive" etc etc - there surely must be something quite significanly wrong for it to be that different. I get better figures from my C270CDi auto Merc.
Edited by Bill Payer on 11/01/2010 at 23:00
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Yes, there must be something wrong. My Pug 207 SW 1.6 averages 62-64 long term, and like you I have confirmed the computer's calculations with my own. Do Pug and Ford still share diesel engines? I should expect a city stop-start diesel to manage 42 mpg?
Edited by Andrew-T on 11/01/2010 at 23:09
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Can't comment on this particular engine but I've read that the most realistic figure to expect is somewhere around the claimed urban mpg and not the rather more artificially derived average.
Having said this, my recent experience of 2 modern upmarket diesels: one struggled to give even the claimed urban mpg as an average (a situation like yours I suspect) whereas the other gets the claimed average mpg or better, my driving style is the same..... I've never experienced this sort of variation with petrol cars either.
Comments on not using the turbo (i.e. keeping the revs down) are good advice and tbh I find that I get better mpg on Shell or Sainsbury's City Diesel than I do with other makes, worst in my experience is from Morrisons for some unknown reason with perhaps a 4mpg difference between worst and best in similar motoring.
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How many miles has the car done?
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My uncle has the same engine in a C3 and gets around 56mpg.
I have the 110hp version in my C5 Tourer and that is showing 50mpg over the first 500mls despite being a new tight engine and doing shorter runs in this bad weather.
I can't think how you could drive the Fiesta hard enough to drop to 44mpg on a long run. Has it ben checked for any faults?
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You need to calculate the consumption over a reasonable length of time, say a month minimum, to get a valid average. Even then you'll find that the consumption will vary month by month and from one season to another.
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can I throw further confusion into this thread ?
I have found with my car that the fuel economy can be terrible if driving off turbo (too low revs).
I think these smaller engine capacity diesels need to be driven on boost to achieve somewhere near the quoted figures.
The engine in my car, 1.5l turbo diesel.
I did drive to Wales and back once at mostly 70mph with four people and got 56mpg.
Yet in this bad weather on fresh snow I have mainly been driving off turbo letting the torque pull the car through the gears and got a miserable 46mpg !
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I assume the OP has a New car.
And he says "I generally keep within the speed limit, don't accelerate like a nutter"..
And I suggest his car has done under 10k miles...
So if correct, the engine is still tight and the way he drives it will never be broekn in as he drives too gently..
How many miles?
How often do you drive over 3,000rpm for 10 minutes.?
How often do you accelerate to 4,000 rpm.?
I always accelerate in low gears over 3,000 rpm..
Edited by madf on 12/01/2010 at 11:09
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So if correct the engine is still tight and the way he drives it will never be broekn in as he drives too gently..
Indeed, modern engines do not require running in ? ignore the handbook, just don't continuously thrash them to within an inch of their lives, if anything drive a little harder than normal for the first few hundred miles. Plenty of revs with light throttle openings.
There a danger with modern engines that you'll either glaze the bores or end up with sticky piston rings from running the engine too gently when new. With a new car or bike I always find a nice stretch of empty road then boot it in 3rd gear to about 80% of maximum revs, then lift off the throttle and let the engine braking alone slow the vehicle to just above tickover, repeat twice more. This frees the rings up nicely and sucks them onto the cylinder surface. All my vehicles always register at the top-end of manufacturer's cylinder compression pressure figures because this is how I bed them in. When I used to service cars, the worst engines were always driving school cars, they spend their lives at low revs, killing camshafts and polishing bores causing piston blow by.
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Indeed modern engines do not require running in
HJ's advice: www.honestjohn.co.uk/faq/faq.htm?id=32
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I have found with my car that the fuel economy can be terrible if driving off turbo (too low revs). I think these smaller engine capacity diesels need to be driven on boost to achieve somewhere near the quoted figures.
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Yes by under revving the engine the driver tends to over compensate with too much throttle, the FI dumps fuel into the engine as commanded by the throttle - net result, not getting anywhere fast but burning lots of fuel doing so. Driving like this will also clog particulate filters and will not allow the cleaning cycles to function, this is the reason for most anti-pollution faults on PSA powered diesel cars.
Light throttle openings to prevent too much turbo boost building but allowing the engine to rev into the mid rpm band is the most fuel efficient way of driving turbocharged cars, petrol or diesel. If you mainly do town driving, once a month find a motorway/a-road and give the car a mini thrashing to near the redline one or twice in a high gear putting the engine under plenty of load, doing so may prevent big "anti pollution fault" repair bills in the future. The irony of course is you'll be puffing out nice clouds of soot with full throttle driving to clean the system. The joys of "green" motoring! :-)
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Simple, drive in the "sweet spot" ie point of max torque, most efficient? yes?
Well, it works for me....... 1500 to 2500 covers most of my driving.
i twigged this as my wife would pootle about in 4th ( out of 5) but prob only doing 45mph
and get better MPG than me, HuH?
gerr
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I am far from impressed with the fuel consumption of my new KA. Brochure says that overall/combined fuel consumption is 55 mpg. I am pushed to get 45 mpg although I understand that low temps do not help and HJ says that what you will get in the real work is nearer to the "Urban" figure, which I what I am seeing. Still £35 road tax softens the blow a bit!
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The Ka is a Fiat 500 which is a Panda in party frock. I have a 1.2 Panda which is giving 50mpg under favourable conditions and 45 mpg right now (measured brim to brim). I can't see how the Ka could possibly give 55mpg overall! But you should see an improvement come the warmer weather.
I had a Focus 1.6 petrol that was supposed to do 43mpg, I could never coax more than 39mpg, even on a long trip. Ford are very optimistic with their claims, just like many others.
On the other hand, we also have an Octavia tdi, which averages about 53mpg genuine, very close to the official figures.
Regarding the OP, it does seem pretty poor for a cutting edge small diesel car. No diesel I've ever owned has averaged less than 50 to 55mpg.
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On the other hand we also have an Octavia tdi which averages about 53mpg genuine very close to the official figures.
I was always told that 10% off the official combined figure is about right for typical mixed driving in most cars, but VAG diesels seem to be capable of getting a lot closer.
Our Golf has a combined figure of 52.3 mpg, and tends to average around 50 on the nose, with a record low of 42 mpg (a lot of urban use) and a record high of 61 mpg (law abiding 300 mile run up to Telford and back in minimal traffic). On my commute, I can get it up into the mid 50's without too much trouble, current weather excepted of course.
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I've got a focus with the same engine as the OP and am averaging about 56mpg. Using DP's method: official combined 60mpg - 10% = 54mpg. I'm not doing too bad.
As has already been said, there must be some fault with the OP's van; maybe it just needs a software update.
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Ford are very optimistic with their claims just like many others.
To be fair, as another poster mentioned earlier they're just quoting the government official figures, which are measured on a rolling road - the car isn't 'driven'.
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Thanks for that Bazza. The fact is that the MPG figures are not "claimed" by Ford but are actually achieved in tests carried out, under strict supervision and regulation, by Government Agencies SFAIK. I have made a rod for my own back by buying a full size spare wheel and kit/tools to use it which may have affected consumption adversely even more than the cold weather.I got more like 50 on a steady 200 mile trip on A roads, when the car was new but I have never seen that since.
Sorry - duplicated the learned input of Focus(p)!
Edited by Armitage Shanks {p} on 12/01/2010 at 17:17
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Ford are very optimistic with their claims .............
I got a genuine average 37.3 mpg overall (4899.36 litres in 40215 miles) over 51 months (none of this "over a tankful" rubbish) in my 2 litre petrol 2003 Focus, driven spiritedly. Official "combined" figure 32.5 mpg.
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Same car, same day, same conditions. Here to Norwich the Mrs gets 33MPG coming back I get 39 MPG - its about 90 miles. With the previous Diesel car this read 39 to 49.
A lot is to do with the way you drive. Gear selection, reading the road, lane selection and so on.
Try driving 10 miles at 56 MPH on a level road with a slight tail wind on a dry warm day in top gear and see what you get MPG wise - the official figures have even more perfect conditions.
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Thanks for lots of interesting replies. I have looked on the VCA website and the figures for my car are 54 urban, 72 extra urban and 64 combined. The car has done just under 9000 miles and I've had it from new. I rarely have the a/c on or the heated screens so other than night driving then not a lot of electrical equipment. As one of the posters (diesledogg I think) I tend to drive in the sweet spot where the torque's highest. I conider the car to have been run in correctly with no labouring in top gear or screeming in the lower gears but giving the engine the right amount of work to do at the right engine speeds. I do accept that I need to measure the consumption over more than just one tankful which I will do over the next few weeks. I'll also try different brands of fuel rather than the Tesco stuff I normally use. If it still shows the same consumption over the next few tanks then I'll book it into Ford to be looked at. On my next long motorway trip I'll see how many miles I can squeeze out of it by sticking to 60 for as long as I can.
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cabsmanuk, just a tip from another thread that has been discussed recently.
Diesel fuel has additives from October to March (so that the diesel does not freeze).
The down side to this is a slightly increased fuel consumption.
Hence the fuel economy for most diesel cars is lower in winter.
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Hence the fuel economy for most diesel cars is lower in winter.
I suspect the main reason for increased fuel consumption in the winter is cold weather. Cold weather = denser air, denser air requires more fuel to maintain the correct fuel/air ratio, all modern FI systems have ambient temperature sensors and will increase injector duration to compensate for the cooler inlet charge. Of course mass air flow sensor systems don't require this compensation because, by their nature, they compensate automatically as velocity carburettors used to do.
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ambient temperature sensors and will increase injector duration to compensate for the cooler inlet charge
Don't these mix in some warm air from around the exhaust manifold to help keep the temp up?
Another thing to check: is the engine coolant getting up to full working temperature on the gauge? (if it's got one?)
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SFAIK engine intake air doesn't come from anywhere near the exhaust manifold. In diesels the intake is, for some reason, very low down under the engine which is why diesels are prone to being wrecked by being driven thru shallow floods. I can recall when cars had a pancake shaped air cleaner on top of the engine which had an intake which could be turned to take in air which had come thru the radiator ie a bit warmer plus helped to stop carb icing
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As most diesels have a turbo which compresses air and heats it up... warm air intake is not am issue..
Yaris air intake is as high as engine rocker cover.
Cold gearbox oil does not help fuel consumption...
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I once looked up how the manufacturers' official figures are actually obtained, and it's an eye-opener. IIRC, it goes something like this: CO2 output is measured at the car's exhaust during a standard cycle on a rolling road, with adjustments for the weight of the car and aerodynamics (Cd factor). That gives the published CO2 g/km figure. The urban/extra-urban/combined mpg figures are then calculated (never measured at all!) from the CO2 figure, using a standard formula. Whilst this creates a level playing field (in theory), it's not surprising that the published figures are no guarantee of real world fuel consumption, and all manufacturers are careful to have a disclaimer on this.
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DF many thanks for that interseting input! I do agree that what you describe gives a level playing field but equally it makes the pubished fuel consumption figures a nonsense, on the basis that they are "calculated" rather than "observed"!!!!
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I can recall when cars had a pancake shaped air cleaner on top of the engine which had an intake which could be turned to take in air which had come thru the radiator ie a bit warmer plus helped to stop carb icing
My old Sierra had such a device, except the "winter" air intake came from directly over the exhaust manifold. There was a flexible metal pipe which connected the air filter housing to a collector device spread across all four manifold pipes.
It made an appreciable difference to engine warm-up time in winter, and also fuel economy.
I thought this was an excellent idea, and like most excellent ideas, brilliant in its simplicity.
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Forget single journeys, forget brim to brim, and forget trip computers. The only way to get anything like a valid average consumption is to record every drop of fuel bought and the corresponding odometer reading and then calculate the consumption over a period of 12 months. That's the only way you'll iron out variations caused by driving style, journey differences, and weather differences. If you look at monthly figures you'll see significant differences (several mpg) between summer and winter.
Edited by L'escargot on 13/01/2010 at 10:27
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The trip computer in our old Scenic was accurate to within 0.5 mpg on a brim to brim basis. I was happy from that point to let it keep track of the average over our 18 month / 26,000 mile ownership period (42.8 mpg)
Edited by DP on 13/01/2010 at 10:30
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I am also having similar problems with my fiesta 1.6 diesel. I bought it just before christmas and am beginning to regret it. I compared the tech spec to my 1.5 dci clio and they seemed to be on a par but again am only getting 41 mpg on the car computer. I am equally disappointed to find that when I fill up I get on average 350 miles out of a tank of diesel, although my clio was 55 litre taken (opposed to the fiesta 45) I got 640 miles out of a tank of diesel. Can anybody else advise me on average what they get. The car is going in the garage on monday but I don't think they will find any faults if cabsmanuk has the same problem
Edited by brookie on 16/01/2010 at 14:59
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I bought a new Fiesta Edge 1.25 petrol just before Christmas and am very dissapointed with fuel consumption. Based on three full tanks it has returned 40, 37 & 40 MPG. I was expecting nearer the 50 quoted. The car was partly bought on this expectation. We live in a rural village, both recently retired and most journeys are reasonable distance and little or no involvement in traffic jams etc. I have always found my driving to return good economy (Rover 25 1.4 petrol gave average 41mpg, Skoda Felicia Diesel 53mpg).
Is anyone else had similar experience?
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Will, The much maligned Rover K series in 1.1 and 1.4 form is one of the most efficient petrol engines ever in a car that is lighter than most modern cars. Sadly not many manufacturers go the light/efficient route any more. The only major exception I can think of is Daihatsu with their light and efficient Sirion (50+ mpg out of a petrol engine) with a nod to the excellent FIAT Panda.
The Fiesta is an excellent refined driver's car, but you pay for that at the pumps.
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Can someone please put in big letters somewhere for people that new cars dont often give the stated mpg figures nor are the figures representitive of real life economy... its getting boring reading such comments. When the car has 10,000-15,000 miles, report back.
My wifes car was doing 38 mpg average when brand new. Now with 17500 miles on it, its doing a regular 43-44 mpg. Official figures are a combined of 44.8.
Count yourselves lucky you dint buy a hybrid - then you would be complaining about not getting your official figures!
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Agree with Stu.
My diesel averages 58mpg. It's 7 years old and done 45k miles..
The official average is: 57mpg.
If the car has done less than 10k miles, you will NOT achieve official figures.
It helps of course if you drive it hard..
Do any of the complainants drive their cars hard? Over 3500rpm? Accelerate hard? 70mph on motorways for tens of miles non stop?
Anyone who has bought a car since December 2009 has hardly had a chance to with the snow and ice..
You need to give it some prolonged stick - over several weeks and thousands of miles.
Then see the consumption improve.
If you are driving a new car to get best fuel consumption, you will not achieve it...It needs to be bedded in = by some hard running in.
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madf, that sounds counter productive. Driving hard for several thousand miles will increas fuel consumption significantly during that time. Surely the last thing the OP wants?
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So iffen I keep the Galaxy another 10 years / 200,000 miles I should be getting around 75mpg?
Yes?
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Alanovich
You need to bed in the engine surfaces. The quickest way to do that is some mixed hard driving. Prolonged driving at low throttle opening and minimal load can lead to cylinder bores never bedding in .. and hence poor fuel consumption - for ever..
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I'm dismayed that our new Honda Jazz is only doing 48MPG when the old one did 50. :)
This is semi-rural and round town motoring.
I don't buy this "bedding in" etc. Engine builders talk about the first 50 miles being critical - the engine has probably done that when you get it.
I've run company cars to high mileages with fuel monitored on spread-sheets and can't recall any noticeable changes over time.
Edited by Bill Payer on 21/01/2010 at 16:09
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. For the first 1,000 miles do not exceed 3,000rpm, but make sure you reach 3,000rpm regularly. For the next 1,000 miles (to 2,000 miles) do not exceed 3,500rpm, but make sure you reach 3,500rpm regularly. For the next 1,000 miles (to 3,000 miles) do not exceed 4,000rpm, but make sure you reach 4,000rpm regularly. For the next 1,000 miles (to 4,000 miles) do not exceed 4,500rpm, but make sure you reach 4,500rpm at least a couple of times a week.
After that, no limit, but make sure you continue to hit 4,500rpm through the gears several times a week. The benefit of this is it helps to self clean the injectors, it blows any accumulated soot out of the exhaust system and it helps to free off the piston rings, making the engine more efficient and less likely to use engine oil.
www.honestjohn.co.uk/faq/faq.htm?id=32
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All this rpm stuff is nonsense, HJ sourced or not. Modern engines do not need running in, if anything rev them harder than you normally would for the first few hundred miles, plenty of revs but just not full throttle. Cricky the most highly tuned motors of them all (Jap superbikes) are held against the rev limiter full-throttle in neutral as they roll off the production line to "test" for manufacturing faults! You can knacker an engine or drastically reduce its service life by running it too gently when new, it'll take being driven hard - if anything you'll end up with a better engine as a result.
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I agree with Steve Lee. The engines that I've seen produce most bhp and with best torque spread on the dyno have been driven hard from day one. In fact the fastest and best way to bed in new piston rings is to use large throttle openings at lowish revs because the high combustion pressures thus generated push the rings hard against the bore without generating lots of heat from excessive revs.It's this pressure that ensures good ring/bore contact, not the "springy" radial pressure inherent in a piston ring.
This approach does put more load onto the bottom end of the motor, but unlike engines from the past, modern engines are so well made that I've never seen problems from such an approach.
Well bedded in rings produce more power with lower oil consumption and lower oil contamination.
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If I had bought the car with my own money could I take it back to Ford demanding my money back because there's no way this vehicle will achieve anything like the fuel consumption they claim? >>
www.vcacarfueldata.org.uk/faq/
Q: My vehicle does not produce the same fuel consumption figures as shown in the 'New Car Fuel Consumption and Emission Figures' publication and/or the Internet site.
A: Because of the need to maintain strict comparability of results achieved by the standard tests they cannot be fully representative of real-life driving conditions. Firstly, it is not practicable to test each individual new car; thus only one production car is tested as being representative of the model and may therefore produce a better or worse result than another similar vehicle. Secondly, there are infinite variations in driving styles and in road, car and weather conditions, all of which can have a bearing on the results achieved. For these reasons the consumption achieved on the road will not necessarily accord with the official test results.
Q: I appreciate that the official fuel consumption figures are obtained under controlled test conditions and as such may not be fully representative of real-life driving conditions. However, I am concerned that the figures achieved by my vehicle are radically different to the official figures.
A: You should refer to the 'Hints for Less Environmental Damage' which outline ways of optimising fuel economy. If, following observation of the recommended points, fuel consumption remains higher than you would expect this may indicate a fault with your vehicle and you should ask an authorised dealer or other competent organisation to examine it.
Q: How is the fuel consumption test conducted.
A: The test is outlined in Directive 93/116/EC and provides results that are more representative of actual average on-road fuel consumption than previous tests. There are two parts: an urban and an extra-urban cycle. The cars tested have to be run-in and must have been driven for at least 1,800 miles (3,000 kilometres) before testing.
Urban Cycle:
The urban test cycle is carried out in a laboratory at an ambient temperature of 20oC to 30oC on a rolling road from a cold start, i.e. the engine has not run for several hours. The cycle consists of a series of accelerations, steady speeds, decelerations and idling. Maximum speed is 31mph (50km/h), average speed 12mph (19km/h) and the distance covered is 2.5 miles (4km).
Extra-Urban Cycle:
This cycle is conducted immediately following the urban cycle and consists of roughly half steady-speed driving and the remainder accelerations, decelerations, and some idling. Maximum speed is 75mph (120km/h), average speed is 39mph (63 km/h) and the distance covered is 4.3miles (7km).
Combined Fuel Consumption Figure:
The combined figure presented is for the urban and extra-urban cycle together. It is therefore an average of the two parts of the test, weighted by the distances covered in each part.
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further to my last e-mail last week, my fiesta has been in the garage and they have fitted a new sensor/upgraded the software on the trip computer, I am now getting more realistic readings, travelling on the M1 in the 50mph speed limit for 10 miles I did get the mpg to average at 57, and subsequent travel at 60/70 mph did still average over 50 mpg on the computer, so happier at present. Cabsmanuk, suggest you get your garage to look at yours too.
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Sounds like they've just meddled with the odometer to make the car seem to be more efficient, or am I being cynical/ ;-)
An Aussie magazine took a new Fiesta Econetic from Darwin to Adelaide (3000km?) and achieved 70-odd mpg which impresses me. Mind you on such economy runs they often leave the air-con switched off, and I doubt that there is much urban stop-start traffic in the outback!
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Oh my goodness, what is it with people relying on a trip computer to give accurate readings?
My wifes car has one, but it is never anywhere near the true brim to brim figures and what it says can only be taken with a grain of salt.
Are people just too lazy to note their mileage/litres used down and get a calculator out?
One assumes that if we can reprogramme a trip computer to show an 80 mpg average, everyone will be happy then!
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........... what is it with people relying on a trip computer to give accurate readings?
I know my Focus trip computer is inaccurate.
Firstly, the average consumption indicates to 0.1 mpg but the actual figure always alters in increments/decrements of 0.5 mpg. The tenths figure is always 2 or 7.
Secondly, the "miles remaining" figure is inaccurate. Immediately before I fill up I add the distance travelled since the last fill up to the "miles remaining" reading. This should give the range of the tank based on the current average consumption. Immediately after I fill up I note the "miles remaining" figure, which should be based on the same average consumption. The "immediately before fill up" figure is invarianly 60 miles more than the "immediately after fill up" figure, even though the car hasn't moved! I always fill the tank as full as I can possibly get it, so it's not related to that.
My previous similar variant Focus did exactly the same.
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Sniff
Buy a VW group vehicle then.
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Buy a VW group vehicle then.
I'm quite happy to accept that my car's trip computer is just a toy. It wouldn't bother me if the car didn't have one. What real use are any of them?
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Odd..... the mpg on our Citroen C3/C5 displays are within 1mpg of tank-to-tank calculations.
The remaining mileage figure does jump about by 10 miles or so at times though.... travelling and it might show 70mls left... park up then start off tens mins later it shows 60mls remaining.
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Firstly the average consumption indicates to 0.1 mpg but the actual figure always alters in increments/decrements of 0.5 mpg. The tenths figure is always 2 or 7.
I don't think that's technically 'accuracy' - precision?
The computer could only be described as 'inaccurate' (ie. not as accurate as it could be) if the displayed value was more than 0.25mpg off your (presumably accurate) calculated figure. Is it?
EDIT: I guess it probably is
Eg.
displayed=30.2, actual=30.3 - ok
displayed=30.2, actual=30.5 - inaccurate (display should be 30.7)
Edited by Focus {P} on 22/01/2010 at 10:35
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I don't think that's technically 'accuracy' - precision?
Let's just say it casts doubts on its accuracy.
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Let's just say it casts doubts on its accuracy.
Fair enough, but to me it doesn't - I doubt it is accurate from what I've read on this site (I've never checked it), but the fact that the tenths digit is only a 2 or a 7 doesn't come in to it as far as I'm concerned.
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The range calculation is based on how the vehicle has been driven over the last few miles, road conditions will obviously come into play too, hills etc.
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The range calculation is based on how the vehicle has been driven over the last few miles road conditions will obviously come into play too hills etc.
The 60 miles change occurs when the car is stationary, so the mpg figure for the last few miles won't have altered from what it was before filling up to what it is after filling up.
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but the fact that the tenths digit is only a 2 or a 7 doesn't come in to it as far as I'm concerned.
One second it's 2 and the next second it's 7. Always. It can't always be truly 2 or 7 and the true figure can't change by that amount instantaneously.
And what about the range of the tank changing by 60 miles at filling up time when the engine isn't even running or the car moving?
Edited by L'escargot on 22/01/2010 at 15:09
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Perhaps filling the car up resets the trip computer to start working off a pre-determined set range? This is presumably to stop the trip computer coming out with daft figures, ie if you rolled down a long hill and stopped for fuel at a garage at the bottom the calculated range would probably be about 2,000 miles based on the average fuel consumption of the last few minutes!
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Testing to get the manufacturers cold start figures has to be between 20 to 30C.
So a manufacturer can test at the tropical figure of 30C (you would If you could - wouldn`t you?)- while we are living at around 5c or worse at the moment. Talk about massaging figures for self benefit. I wonder who did the lobbying to get `cold start` tests at 30C?
tinyurl.com/5fuamf
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Forget the absolute figures, forget comparing the numbers in the brochure with those on the dashboard mounted gimmick, forget about comparing them with meticulously kept tank to tank records - use the published numbers only to compare one car against another.
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Forget the absolute figures forget comparing the numbers in the brochure with those on the dashboard mounted gimmick forget about comparing them with meticulously kept tank to tank records - use the published numbers only to compare one car against another.
I agree with all that, but I would add that if you really want to know the average fuel consumption of your car (making your journeys and with your driving style) you have to keep meticulous records and calculate the average consumption over periods of a year to iron out variations caused by the weather.
Edited by L'escargot on 23/01/2010 at 07:51
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Testing to get the manufacturers cold start figures has to be between 20 to 30C. So a manufacturer can test at the tropical figure of 30C (you would If you could - wouldn`t you?)- while we are living at around 5c or worse at the moment. Talk about massaging figures for self benefit. .............. tinyurl.com/5fuamf
All the information surrounding the test parameters is there ~ for anyone sufficiently interested (or intelligent) to look. Nothing is massaged, hidden, or omitted.
tinyurl.com/67sdyr
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One second it's 2 and the next second it's 7. Always. It can't always be truly 2 or 7 and the true figure can't change by that amount instantaneously.
No, I understand that. In that situation I would assume that the figure it was trying to display was midway between the two. Eg. changing between 32.44 (displays 32.2) and 32.45 (displays 32.7).
So the display limitation of only showing 2 or 7 limits the precision of the indicated mpg, but it doesn't mean it isn't 'accurate' ie. showing the correct value given the display limitation.
But I'm also happy to accept that you could also describe the system as 'inaccurate' by your definition - just explaining an alternative viewpoint :-)
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So the display limitation of only showing 2 or 7 limits the precision of the indicated mpg but it doesn't mean it isn't 'accurate' ie. showing the correct value given the display limitation.
The other digits are there, but they only show once in a blue moon and then only transiently and you have to be lucky enough to be looking at the readout at the instant they are showing.
99.9% of the time it's either 2 or 7.
Edited by L'escargot on 23/01/2010 at 07:44
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So the manufacturer lets the car heat soak in the lab at 30C. The oils in the engine and gearbox are less resistive due to the heat lowering the viscosity. It`s then started (only once) and put through it`s official cycle - no doubt with either the manufacturers best test driver on the throttle or a computer program operating engine speeds.
You can speculate on what they may get up to - to massage the MPG figures. The `one in a thousand` engine - or special oil - perhaps a tweak of the ECU software.
It`s like a camel that died within 50 yards of a waterhole - but it`s being levered forwards to make it 45.
Dropping just 1mpg could be commercial suicide in the market place and the whole of the manufacturers organization hold their breath - as what tricks can be done, are done.
Auntie Nellie then looks at the figures in the showroom - not realizing that they were generated in temperatures more representative of Equatorial Africa.
The amazing thing is that anyone gets within 10mpg of official figures - and while of course it`s true that the only meaningful use of the figures is to compare one car with another - the actual test parameters could have been more honest in reflecting European Winter temperatures.
Running a `Winter test` figure at - say 5C (also multiple cold starts) would really show how the 30C test favours petrol engines by assisting their weakness over diesel - in needing enrichment at low temperatures.
Edited by oilrag on 23/01/2010 at 08:26
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Measured brim-to-brim over that last 27830 miles (from new) my TT 2.0TFSI has averaged 36.2mpg against a government figure of 36.7mpg. The low has been 28.4mpg and the high 46.2mpg. I do a daily 7 mile commute to work on a mix of country lanes, A-Roads and B-Roads. Otherwise it's local running under 5 miles and long trips to the Midlands from Glasgow pretty much. I'd call that figure fairly representative of what the car can do to be honest - I don't hang around either, most journeys involve using the potential acceleration of the car.
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Measured brim-to-brim over that last 27830 miles (from new) my TT 2.0TFSI has averaged 36.2mpg against a government figure of 36.7mpg. The low has been 28.4mpg and the high 46.2mpg.
I assume you've calculated the overall average properly by dividing the 27830 miles by the total of all the individual amounts of petrol. If so, congratulations. Not many people calculate (or quote) a true overall average.
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Running a `Winter test` figure at - say 5C (also multiple cold starts) would really show how the 30C test favours petrol engines by assisting their weakness over diesel - in needing enrichment at low temperatures.
There's a limit as to how much information can be usefully provided. Most people don't seem to understand the significance of the current information, so adding further information would only increase the confusion.
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The other digits are there but they only show once in a blue moon
Now that is interesting - I'm intrigued. I'm going to monitor mine to try to work out what's going on; hadn't really paid much attention to it before,
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Ford are very optimistic with their claims just like many others.
I have an 8 year old Ford Ka, with stated 42mpg combined fuel consumption. I used to regularly get ~48mpg and struggled to get as low as 40mpg. But short journeys and traffic are absolute killers. Winter seems particularly bad, possibly due to shorter journeys, and warming up the engine. These days I probably get near to 40mpg. Maybe age is catching up with it, maybe the windy local lanes. No doubt driving style plays a role e.g. anticipation and natural slowing rather than regular braking. And I turn off the engine at many junctions with long light changes.
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In the early days of gov figures they were given as town, 56mph & 75mph. I found it far easier to work out what figure I could expect using a combination of these. I wonder if they were real life or lab figures?
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Well per an article I read recently in an unremembered car magazine some of the less scrupleous manufacturers hit on the wheeze of a special engine managment unit that "recognised" the test configuration and went into a special mode ( which if I understood would have been useless in a real world situation) for the duration of the test.
Hence achieving unrealsitically low CO2/high MPG
Scheesh!
But regardless I only use the Government figures for comparison between models or makes or engines /gearboxes
Edited by dieseldogg on 26/01/2010 at 09:48
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