Sudden drop in MPG - 330d 2002
Discussion
I've had a sudden drop in mpg on the on board computer. I hadn't reset it for at least a month and it dropped from 41-42mpg to 37-38mpg overnight...
I had a pair of Goodyear F1's fitted on the rear two days ago and when I arrived home (15 miles) and noticed that the mpg had drooped! I know it aint really going to be the tyres, but it's just a fact that I noticed then - I do tend to keep an eye on it. 99% of the time it's the selected 'function'.
Otherwise it drives fine, had some foot to the floor time today - no change!
What sensors could cause something like that? I did reset it this morning - before the foot to floor moments and it just showed 38 or so whilst cruising. Usually it would show nearly 70 then climb down to the 42 that I normally get.
Bloody Cars!
I had a pair of Goodyear F1's fitted on the rear two days ago and when I arrived home (15 miles) and noticed that the mpg had drooped! I know it aint really going to be the tyres, but it's just a fact that I noticed then - I do tend to keep an eye on it. 99% of the time it's the selected 'function'.
Otherwise it drives fine, had some foot to the floor time today - no change!
What sensors could cause something like that? I did reset it this morning - before the foot to floor moments and it just showed 38 or so whilst cruising. Usually it would show nearly 70 then climb down to the 42 that I normally get.
Bloody Cars!
I know it sounds daft but have you checked the pressures in the tyres? The guys at the tyre fitters rarely check the correct pressure for you car from my experience.
I had a 120d with run flats that I didn't check the pressures on for ages, when I checked them they were all a bit soft and when inflated to proper pressures I was getting 5mpg more(from 44.9 to 50.4 according to trip computer).
I had a 120d with run flats that I didn't check the pressures on for ages, when I checked them they were all a bit soft and when inflated to proper pressures I was getting 5mpg more(from 44.9 to 50.4 according to trip computer).
It's the tyres. The Eagle F1 is a very grippy tyre offering outstanding performance. As an unfortunate consequence of this, it also has a reasonably high rolling resistence which hampers fuel economy.
Moving our 530d from Conti EcoContact's to Eagle F1 also dropped the MPG from about 42 down to 39 over the same sort of trips. I also lost about 10% from my 530i moving from Dunlop SP Sport 2000E's to the F1's.
Moving our 530d from Conti EcoContact's to Eagle F1 also dropped the MPG from about 42 down to 39 over the same sort of trips. I also lost about 10% from my 530i moving from Dunlop SP Sport 2000E's to the F1's.
No, no no!! Roling resistance would never be that significant.
Bridgestone have recently 'outed' Michelins claims for improved MPG on one of their tyres which was supposedly due to it having low rolling resistance. Extensive testing by Bridgestone has shown that low rolling resistance has a negligible effect on fuel consumption and that the Michelin tyre was no better than a range of others.
I have seen the same effect on my 320D, and worried the same. I bet if you reset just before a longish (say 300 miles or so) run, you will establish a decent figure that will then stay the same with mixed driving.
Bridgestone have recently 'outed' Michelins claims for improved MPG on one of their tyres which was supposedly due to it having low rolling resistance. Extensive testing by Bridgestone has shown that low rolling resistance has a negligible effect on fuel consumption and that the Michelin tyre was no better than a range of others.
I have seen the same effect on my 320D, and worried the same. I bet if you reset just before a longish (say 300 miles or so) run, you will establish a decent figure that will then stay the same with mixed driving.
"Bridgestone presented the results of an experiment testing Michelin’s promise of reduced fuel consumption when using their Energy tyres. The experiment was carried out at the behest of one of its carrier customers and, as a result, involved head-to-head performance comparisons with Bridgestone’s own conventional tyres.
The initial results, said Bridgestone, showed no significant differences in the performance of each tyre. However, Michelin were quick to dispute this conclusion, citing 70 tests involving tyres from both organisations, where the Michelin tyre came out on top in terms of fuel consumption and criticising the methodology of the tests, in which the company was not involved.
The test itself consisted of the fitment of new and 50% worn tyres from each company to four identical vehicles. Drivers were then required to make the same 400km per day journey and, after two months, the tyres were swapped for another two months.
“After four months,” summarised Bridgestone France Technical Director Olivier Monbet, “it was not possible to demonstrate a difference in terms of consumption between Bridgestone and Michelin.”
Monbet, autoactu.com reports, went on to qualify this statement, suggesting that the effects of tyres on fuel consumption could easily be neutralised with other factors, such as driving style, aerodynamics and vehicle maintenance. The results appeared to have drawn into question the idea that tyres with lower rolling resistance could impact meaningfully on fuel consumption."
The initial results, said Bridgestone, showed no significant differences in the performance of each tyre. However, Michelin were quick to dispute this conclusion, citing 70 tests involving tyres from both organisations, where the Michelin tyre came out on top in terms of fuel consumption and criticising the methodology of the tests, in which the company was not involved.
The test itself consisted of the fitment of new and 50% worn tyres from each company to four identical vehicles. Drivers were then required to make the same 400km per day journey and, after two months, the tyres were swapped for another two months.
“After four months,” summarised Bridgestone France Technical Director Olivier Monbet, “it was not possible to demonstrate a difference in terms of consumption between Bridgestone and Michelin.”
Monbet, autoactu.com reports, went on to qualify this statement, suggesting that the effects of tyres on fuel consumption could easily be neutralised with other factors, such as driving style, aerodynamics and vehicle maintenance. The results appeared to have drawn into question the idea that tyres with lower rolling resistance could impact meaningfully on fuel consumption."
DSM2 said:
No, no no!! Roling resistance would never be that significant.
I'm can understand that. I guess that the Goodyear F1 wouldn't have lasted for (guesstimate)10 years if they were crap on MPG!?I've never seen the ave MPG drop below 40 except that time when I full bored it up some serious hills for a hour or so...
Just out of interest (and not reading the manual) what is the ave mpg actually telling me? Ave over last hundred miles, ave since reset last pressed....etc....?
nobrakelights said:
I'm can understand that. I guess that the Goodyear F1 wouldn't have lasted for (guesstimate)10 years if they were crap on MPG!?
Eagle F1 is a high performance tyre aimed at drivers who value grip over longevity and economy. Therefore the impact on MPG is not an issue to the tyres target market.[quote]Just out of interest (and not reading the manual) what is the ave mpg actually telling me? Ave over last hundred miles, ave since reset last pressed....etc....?
[TW]Fox said:
nobrakelights said:
I'm can understand that. I guess that the Goodyear F1 wouldn't have lasted for (guesstimate)10 years if they were crap on MPG!?
Eagle F1 is a high performance tyre aimed at drivers who value grip over longevity and economy. Therefore the impact on MPG is not an issue to the tyres target market.[quote]Just out of interest (and not reading the manual) what is the ave mpg actually telling me? Ave over last hundred miles, ave since reset last pressed....etc....?
Improved grip will equal improved fuel consumption as the tyre is transmitting power more efficently. Narrow tyres will improve consumption because of less drag, tyre pressures will also have an effect.
When the tyres were changed the overall diameter changes, this will impact on consumption as the overall gear ratio changes. As the diameter changes the revs/mile changes. Changing tyres to new tyres of the same brand will increase the diameter by approx 12mm. If the tyre is changed for a different make this can have a much more pronounced effect as the difference in diameter can vary by a larger figure. This is why you can see a difference of 2 to 5% in mpg. Also the OBC is not particular accurate, to check mpg it should be done on brimming the tank and measure mileage between fills.
Edited by KenD on Sunday 27th July 08:10
When I swapped from Bridgestone run flats to Falken FK452's I noticed a 4mpg drop as well.
Check your pressures though, being at 2.4 bar instead of 2.8 bar can make more of a difference.
The OBC calculates the last 999 miles as a continuous cycle until you reset it, so it only remebers the last 999 miles.
So reset it and see what happens.
Check your pressures though, being at 2.4 bar instead of 2.8 bar can make more of a difference.
The OBC calculates the last 999 miles as a continuous cycle until you reset it, so it only remebers the last 999 miles.
So reset it and see what happens.
I switched from the Nokian (budget?) tyres that came with my car when I bought it to 4 new Goodyear Eagle F1s six weeks ago and have since experienced a drop in my average MPG from 50-51 down to 44! During those six weeks it's had a major (40,000 mile) service and checked tyre pressures regularly.
I couldn't believe that tyres would make such a difference but after reading this thread it seems to suggest they can!
The Goodyears are noticeably more grippy than the original tyres - superb in the wet, not sure what I'll do when I replace next time!
Onz (Golf TDi Owner
)
I couldn't believe that tyres would make such a difference but after reading this thread it seems to suggest they can!
The Goodyears are noticeably more grippy than the original tyres - superb in the wet, not sure what I'll do when I replace next time!
Onz (Golf TDi Owner
)Fox- said:
I'd rather know that in the event of having to take evasive action or stop quickly I've got the best possible chance re: tyres than get a few extra mpg, but perhaps thats just me 
Don't get me wrong - I think the tyres are fantastic, I was just surprised at the difference in fuel consumption! Fox- said:
I'd rather know that in the event of having to take evasive action or stop quickly I've got the best possible chance re: tyres than get a few extra mpg, but perhaps thats just me
Well I'm talking about the difference between a quality Goodyear product and an equal quality Michelin product that could give me my 4 mpg back (or more)- that's approx 7 quid per fill up I'm throwing away because I didn't see any reports mentioning the drag of these F1's. Do they mention these figures in tyre tests or does it depend on which magazine I'm reading?I bought a diesel for its economy, it's bearly worth having if it's only giving 38mpg dues to a bad tyre choice! Maybe I should turn them round as they're directional and see if I get 46mpg? Woo hoo!
nobrakelights said:
Well I'm talking about the difference between a quality Goodyear product and an equal quality Michelin product
The Michelins are not equal products - have a read of either Autocar or Evo's tyre tests where they benchmark the tyres. The Pilot Sports are considerably worse in the wet - in stopping from 70mph they take a further full two car lengths to pull up. Both tests measure rolling resistence as well to give you an indication of fuel economy.Gassing Station | BMW General | Top of Page | What's New | My Stuff