Just wondered if anyone else out there has experienced a recent fall in their MPG? My wife and I have noticed a fall in the MPG of our two very different cars. Mine is a Honda Accord Tourer 2.2CDTi, which I have had since new in 2006. Its MPG has always been averaging 42 MPG. Now in the past couple of weeks its MPG is struggling around 39 MPG.
My wife's Mondeo 2.0 Zetec has done exactly the same, it has dropped from 37 MPG to 34 MPG.
Very odd as nothing else has changed apart from the price of fuel. No change to our journey patterns, no change to type of petrol or diesel used, or where we buy the fuel, yet both cars are using more fuel.
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The weather is now colder & you are now driving with headlights on, demisting fan going full blast and more use of wipers or heated rear screen?
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Can you rule out the winter effect - cold weather, lower tyre pressures (unless checked frequently), longer to warm up, lights, more traffic jams, age of tyres?
Did have a cold snap couple of weeks ago.
Personally have not seen any major drops in mpg since I readjusted tyre pressures - what was 2.15 bar in the summer, is 2.05 bar in the cold, so when re inflated to correct pressure
mpg difference between summer and winter went from 1 mpg to less than 0.5mpg.
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My difference in' computed' mpg. between the height of summer and now is about 4 mpg and I attribute most of this to the temp difference and not the use of accessories.
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I can tell the difference between driving in Benelux/N France, and driving here. MPG is 5%-10% higher on the flat, open continental roads.
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It is all very odd. Neither my wife or myself noticed such a change last year, when we still had our respective cars. It has only happened with the last two tankfuls of fuel in our cars.
Both cars are on relatively new tyres, under 5,000 miles ago, and on the same routes as before.
Just wondered if anyone else had noticed, but at least many of you will now check!
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I wonder if a small percent of bio-fuels have been introduced? This will have an effect on economy, albeit only slightly.
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From about now traffic becomes heavier too. End of school holidays, very few people away etc etc. My commute now takes up to 30 minutes, during the summer it's 15-20. This coupled with colder weather sees an increase in fuel consumption - 40 mpg in summer, I expect mid 30s at this time of year.
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The reason why fuel consumption goes down in winter, is because of the additive put in the diesel to stop it waxing up in cold weather.
When my tractors have the winter diesel, they do not pull as well.
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I think it's price driven. I have noticed a marked increase in traffic density since fuel prices have reduced. Journeys which had become quite tolerable during the height of price increases are once again miserable. Slower traffic with more queueing = fewer mpg.
Despite my high mileage, strangely enough it's costing me money. If I can't get to as many customers during a day on the road I earn less.
Never thought I'd favour higher fuel prices but it sort of worked for me. Don't suppose it would have lasted though. I guess people would have just got used to it in time and we would all be back to square one with the downside of crippling fuel costs for good measure.
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"I have noticed a marked increase in traffic density since fuel prices have reduced"
This is probably a minor effect. More to do with my previous comment re the time of year. High prices also coincided with main holiday periods so people were away.
How many people do you know who go on their main holiday in November/December? If you are like me very few - ironically me and my wife always used to go away this time of year before daughter came along!
Most people who work will be doing so, Christmas isn't far off, annual leave entitlement running out (if on Jan - Dec terms) which leads to much heavier traffic. It happens every year.
Edited by daveyjp on 05/11/2008 at 15:22
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It is the winter additive in the fuel.
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>It is the winter additive in the fuel.<
I can't believe that any genuine 'additive' would be acceptable to all concerned if it increased consumption by ~10%.
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I can't believe that any genuine 'additive' would be acceptable to all concerned if it increased consumption by ~10%.
It's more acceptable than the alternative if we get a really cold spell!
Edited by Harleyman on 05/11/2008 at 19:21
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Christmas isn't far off annual leave entitlement running out (if on Jan - Dec terms) which leads to much heavier traffic. It happens every year.
I seem to remember that statistically there is a Friday in November which suffers the worst congestion of any day of the year. I think I remember Radio 5 doing a piece on it last year on the Friday in question. Third Friday in November, something like that.
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I've just noticed exactly the same thing. I put it down to the car needing servicing - plugs etc, but I begin to wonder now. I must look back through my records and see if this is an annual effect.
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Winter fuel is sold from Oct to Mid-March. Supposed only to make a 3% difference, but when I was doing large distances I always seemed to find it made more than that (even without taking the increased warm-up time, use of electrics etc into account).
Summer fuel turns from liquid to gel around -5C, UK winter fuel extends that to about -15C. Other countries have different formulations.
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I think people get too hung up on repeating fuel consumption within a couple of mpg (If I may be so bold to say). To get a repetative result on an ongoing basis you almost need lab conditions where nothing changes but as some posts above point out we are seeing changing weather conditions that will impact fuel density and ambient air temperature with a number of other things on your car working harder such as the battery and alternator. Although you say Paul that your journeys have not chnaged, in reality they have and always will do as no 2 journeys are the same, there will be variability in there somehwhere, stopping a bit longer at a juntion, arriving at the lights just as they change, slower average speeds due to the weather conditions etc etc. Focusing on mpg to this extent is a waste of time IMO.
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Broadly speaking I agree, but when I was doing the same 400-mile trip a couple of times a week on relatively free-flowing motorways and with cruise control, I was getting very repeatable figures. Summer around 43mpg, winter around 39mpg.
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www.honestjohn.co.uk/forum/post/index.htm?t=40123
Winter diesel switchover - Hamsafar
(4) Subject to the provisions of these Regulations, no person shall, during a period beginning on 10th September in any year and ending on 15th March in the following year, distribute diesel fuel which?
(a) does not comply with the winter diesel fuel requirement; and
(b) is for use within the United Kingdom.
(5) Subject to the provisions of these Regulations, no person shall, during a period beginning on 16th March and ending on 9th September in any year, distribute diesel fuel which?
(a) does not comply with the summer diesel fuel requirement; and
(b) is for use within the United Kingdom.
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I've noticed exactly the same thing - about a 4mpg drop. Put it down to colder temperatures. The Passat only averages 35mpg (computer) on the short run to and from the airport, I hate to think what the 2.0l Accord was actually doing with a cold engine.
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For the last umpteen years I have kept records of every drop of petrol that has gone into my car. I calculate the average consumption for each month and the trend (regardless of the car) is always for the consumption to be worse in winter than in summer.
Edited by L'escargot on 06/11/2008 at 07:25
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I have keept similar records since using company vehicles for over 30 years, you can certainly pick up trends like economy always drops after the first service of a new car, its more fuel efficient driving up to Scotland from Surrey than the return journey. Heavy rain has a dramatic effect and light rain can improve ecconomy.And the old chesnut suppermarket fuel is less efficient--o yes it is.
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Nothing to do with fuel. It's to do with engine warm up times - especially petrol. Distance to warm up is obviously going to be longer when temperature is 5c not 20C...so mixture is richer. Couple that with running lights/hetaer/demister when cold with a rich mixture and fuel consumption in first 2-3 miles has probably doubled.
And cars cool down quicker when stopped.
And air intakes let in heated air from exhaust manifold to precent mixture freezing which means less power.. and so on...
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........ its more fuel efficient driving up to Scotland from Surrey than the return journey.
Even though it's uphill to Scotland, and downhill on the return journey?
;-)
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Thanks everyone for the replies, it seems that a combination of factors is at work here. It is just that I use my instant MPG readout as an indication not only of how I am driving, but also as an advance warning of potential problems.
It was just that my paranoia in the current economic climate wondered if extra revenue was being earnt from the falling price of fuel by diluting it in some way to cause more to be consumed!
Another conspiracy theory bites the dust.
Thanks to all again.
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I've *really* noticed it on the Volvo in recent weeks, and consumption has increased by about 5 mpg and now down to very low 30's.
Scenic is still doing 42-46 mpg depending on use though. No perceptible difference.
Cheers
DP
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Prompted by this thread I measured my mpg today. 400 mile round trip. No difference at all to figures achieved from Aug 1st onwards. Light traffic today though.
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As prices have fallen, I've run the Accord on V-Power diesel for the last five tanks.
Normally I get a pretty consistent 41-42 mpg. Over the five tanks that has climbed steadily until the last got 47. I have no idea why, but that improvement will easily pay the extra 6p a litre, so I'm going to keep experimenting.
Either that, or the car is finally run it at 77k! :-)
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