>>As a comparison and predictor of actual consumption I think the official figures are excellent.
Yes, agree. I'm surprised quite often by the fearless motoring journalist expose that shock!, horror!! - they couldn't achieve the official combined figure - well, hardly sursprising since most of them think they're Lewis Hamiltons & have about as much concern about fuel consumption as anyone on expenses. I manage at least the advertised figure - and often more - and still manage to have a bit of fun. There's one particular (website based, ends in: ***world) motor journalist who constantly (and tediously) exposes the 'sham' of the EU cycle fuel consumption tests - well, learn how to drive matey. Or take into account that you're sitting in the urban cycle longer than the EU weighting and/or driving above 75mph on extra-urban, with unnecessary braking to boot.
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The true mpg of any particular model varies so much because of variations in driving styles and driving conditions.
This is the exact point that these non-official statistics help to verify. If you can take many statistics from many drivers driving the same car over significant mileages, this has got to be a better overall pointer to the cars real fuel consumption compared to the official figures. It is the official figures themselves which prompted me to look elsewhere for data. It is now clear from data from many sources that thye data for my car is wildly optimistic.
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>> The true mpg of any particular model varies so much because of variations in driving >> styles and driving conditions.
While that's true, you're saying it as if they're the *only* reasons. It's long been clear that identical models of the same car can produce significantly different MPG figures.
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The official figures are repeatable, NONE of the other figures obtained by anyone could be repeated accurately - the actual numbers are irrelevant, it's the comparison between models that's the only reason for their publication.
They apply to my real world!
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it's the comparison between models that's the only reason for their publication.
I think the point is that the comparison isn't valid in the real world (which is where we use the cars, after all).
Some cars can achieve their tested figures, and others can't - how do you know which camp the car you're thinking of choosing is in?
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but surely the comparison is valid in the real world? what the official figures let you do is to compare car A to car B. the fact that you may never achieve those figures doesn't matter.
anyway, does it really matter how many mpg you get? does anyone care these days?
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Some cars can achieve their tested figures, and others can't - how do you know which camp the car you're thinking of choosing is in? >>
You tell me, which model's official figures can't be replicated in the controlled conditions of the official test.
Are you suggesting that some manufacturers cheat, are incompetent or don't care?
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Are you suggesting that some manufacturers cheat are incompetent or don't care?
Nope they don't cheat per se, but you'll find that the car they use for the EC economy tests will be stripped of much of the excess weight that is removable without tools i.e. rear headrests, toolkit from boot. The aircon will be totally off, the electrics all off bar those running the engine, the doors and bonnet lines are likely to be discretely sealed with tape to smooth out the car, the oil in the engine will be at the lightest end of the allowable scale published, while the tank won't contain much more than a couple of gallons at the most. It's not even unknown for the driver for the tests to be selected for their stature or lack of it. My colleague is a former designer for a manufacturer and these are just some of the things done.
In general a big engined car is likely to come closer to the stated mpg than a small engined car, because on test the big engine is lolloping, using tons of fuel while the small engine is running about as efficiently as it can. In real life the small engine isn't enough to keep up with traffic so is driven harder than the most efficient point, while the big engine is closer to the more efficient point in normal operation.
I've never had any trouble regularly beating the published figures in the higher powered cars I've owned, but more trouble in the small engined cars. I've never gotten as high as the Extra-Urban figure on a tank to tank job though.
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The cars are tested on a rolling road. What you suggest they do to make a difference is irrlevent to say the least. Tools and head-rest removal irrelevant and not likely to happen :)
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Are rolling roads now in a sero gravity field then?
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Make that a zero gravity field... rolling resistance will be proportional to the weight carried by the car.
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But on a rolling road the car will not have to accelerate the mass of the car, so the only difference would be the rolling resistance of the tyres.
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I've never gotten as high as the Extra-Urban figure on a tank to tank job though.
That's a totally unreliable method of measuring the amount of fuel used anyway. The difference between one full tank and another can be quite a lot ~ unless you've got a Hillman Imp in which the filler neck near enough came straight up out of the tank (no airlocks) and in which you could actually see the top surface of the fuel in the neck.
--
L\'escargot.
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If using the tank to tank method you need to average it over a few tankfulls. As the snail says, the can be quite a difference between fill ups.
I've always used an average over 5 tankfulls to calculate mpg, although I must admit I havn't done that in many years. Maybe someone from a scientific background can expand on the theory behind it and suggest the optimum number of tankfulls to get a reliable result. Anyway, what's the point of doing manual calculations when most cars have a handy little computer that works it out for you.
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You tell me which model's official figures can't be replicated in the controlled conditions of the official test.
I think you're missing the point here - we don't drive in a test lab, we drive in the real world.
Some cars - off the top of my head Diesel Accords and Ibiza 1.2S - are noted for frequently missing their official figures big time.
So say you're trying to decide between an Ibiza and a Colt. The offical figures both show around 50MPG. Yet in real life the Ibiza struggles to do 40, yet the Colt happily does 50. My daughters own both of these cars, but the consumption figures are mine.
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So diesel Accords and Ibiza have rubbish official figures, any more? Who has the "official" list?
Statistically I haven't driven many different cars - but those I have CAN (and do in certain conditions) give me their official figures, even though my normal driving style gives significantly less on average.
For comparison purpose the official figures are fine BUT anecdotally some cars would give a false comparison - great - none of the other published figures can be used for comparison because they're not repeatable. Road test figures include performance testing which many of us simply don't do.
Here's a test, not cheap but I know it works - find a circular motorway route of about 400 miles, pick a time when there's no congestion or roadworks, set the cruise to 70mph using GPS. Check the fuel consumption, fill to fill, using a filling station at the start/finish. On 3 cars I can get within 3-4% of the Extra-urban figures published for those cars so I'm comfortable using official figures to compare these 3 cars.
As expected in weeks when these cars were only used for local commuting and shopping, they give about 20% more than their Urban figure but these aren't the worst congestion conditions around.
As I've said before my overall average is about 96% of the combined figure.
I actually miss the old "75mph" consumption figure as that was a good guide to motorway consumption, of which I did a lot in those days.
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Yes, it is a very impressive site. It gives detail about each cars fill up.
I must be very sad, but my spreadsheet at home showing my fuel economy is very similar to that: graphs, whether it is town, motorway or even country (with the addition of traffic jams mentioned to account for poorer economy) etc. Very detailed.
But I can to a certain extent excuse myself: you see I use a lot of spreadsheets at work and I wanted to polish my skills in them.
Greg
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Has anyone looked up their car on this websit and checked the figures ?
The reason I ask is because in the UK my car was originally listed, by Volvo, as VED C with exhast emissions of 149g/km.
Under the new system it is now rated as band E with 166g/km even though there are a number of owners who have recorded figures under 150g/km.
In this website my car is rated as 140g/km.
Is it possible the figures are being massaged in the UK to move certain cars into higher bands ?
The car in question in this instance is a Volvo S60 D5 (163).
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Is it possible the figures are being massaged in the UK to move certain cars into higher bands ?
The car in question in this instance is a Volvo S60 D5 (163).
Wouldn't surprise me at all - the gubmint is in hock to MondeoMan after all, VolvoMan I'm sure, votes for Cameron ;>
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Wouldn't surprise me at all - the gubmint is in hock to MondeoMan after all VolvoMan I'm sure votes for Cameron ;>
I'm not getting into the politricks debate...but Alistair Darling must have the least wanted job in Britain.
I'm laughing at the thought of the next Budget and his discussion with the new PM.
AD: Gordon, just going to have a play about with the figures here.
GB: No Alistair, you can't do that 'cos you'll send us into the red over here.
AD: Whatabout these numbers then ? Surely they can't hurt.
GB: Ah ! But X is linked to Y.
AD: I'll just plunder the pensions pot again then.
Sorry to go off topic but couldn't help laughing at AD's predicament :))
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Shome mishtake, shurely, Gmac? My manual S60 D5 (2003 MY) has an official output of 171g/km. This may have shifted slightly with the new version of the engine, Euro IV compliance and the like but I can't imagine it's ever gone as low as 149.
CO2 outputs, as we've discussed, are a fairly simple corollary of fuel consumption - for a given fuel type, anyway. So they will vary in the same way from user to user. The official value is just a result obtained under standard - and not necessarily realistic - conditionsto facilitate model-to-model comparisons.
Incidentally, I checked my average consumption over 55,000 miles and found it was pretty well in the middle of the reported range - 6.67 l/100km.
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My model of diesel Passat Estate is reported as getting 5.66l/100km which is 49.91mpg. Now that is more like what I'd expected - not 42mpg most times ( & up to 44mpg in summer).
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Euro IV D5's didn't come in until mid-May 2005 together with a 6 speed gearbox and powerhike to 185 though some EuroIII 163 D5's were still available then along with the 2.4D (163) which is a detuned 185 D5 (who said Volvo had a straight forward line up?).
EuroIV cars have a higher CO2 figure around 174g/km for manual and 199g/km for auto.
My car is a 2005MY EuroIII D5 and the owners doc. shows 166g/km and I have an exhaust gas printout showing 149g/km.
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Exhaust gas printout? Wozzatven? Nothing about it in either of my MoT emissions reports - not that yours will even have had one of those.
I presume the difference between your 166 and my 171 is due to the change to a six-speed gearbox. Out of interest, what's the mph/1000rpm value for that? Mine - in fifth - is a touch over 30 and could usefully be a little higher.
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Ah, wait - only the Euro IV D5s have six speeds? Maybe they just tinkered with the ratios, then.
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