M3 MPG?

[ATB88]

Whattt that's insane! I average ~19-20 mpg's with moderate foot and combined driving.

Yeah, it's frustrating. Especially since the car seems to drive pretty much flawlessly otherwise, so any mechanic that checks the car out just says "everything looks great, you're just driving it too hard to get good MPG", which is false. Sometime this week I'm going to make a new thread about it and put all the information about my situation and what I've done to try and fix it in one place (it was scattered over a few threads in the old forum), and see if anyone wants to take a crack at it with me. A real automotive conundrum.

[Dash1]

Yeah, it's frustrating. Especially since the car seems to drive pretty much flawlessly otherwise, so any mechanic that checks the car out just says "everything looks great, you're just driving it too hard to get good MPG", which is false. Sometime this week I'm going to make a new thread about it and put all the information about my situation and what I've done to try and fix it in one place (it was scattered over a few threads in the old forum), and see if anyone wants to take a crack at it with me. A real automotive conundrum.

Have you dyno'd the car? Do you have an aftermarket tune? Maybe you're running rich.

[Cubieman]

I average 16 mpg highway. I normally stay in 4th or 5th on the highway with 4.10 gears

Do you stay in those lower gear just for better passing ability? I've got 4.10's as well and I'm in 5th for sure if I'm doing >55mph, but that's just for MPG reasons.

[Mystic3]

If it was always serviced be Dinan,did the guy have any internal mods ,cams etc. ?

[ATB88]

Have you dyno'd the car? Do you have an aftermarket tune? Maybe you're running rich.

Car is bone stock, and I flashed the correct stock factory tune onto the DME myself. Did get it dyno'd, made 275 on a dynojet (SAE), which is about where it should be. AFRs for the dyno run looked mostly okay but were apparently pretty rich up at the top end (richer than they should be). But again, the question of why remains elusive.. I've really tried almost everything. I'll get a thread up with more details later this week so I stop polluting this one lol

[mrgizmo04]

I also run 4.10 gears, but in winter the car's just been used for hauling the baby on city/highway and I avg around 22.3mpg.

[mrgizmo04]

Car is bone stock, and I flashed the correct stock factory tune onto the DME myself. Did get it dyno'd, made 275 on a dynojet (SAE), which is about where it should be. AFRs for the dyno run looked mostly okay but were apparently pretty rich up at the top end (richer than they should be). But again, the question of why remains elusive.. I've really tried almost everything. I'll get a thread up with more details later this week

Are your maf and o2 sensors fresh?

[ATB88]

Are your maf and o2 sensors fresh?

Yes and yes

[scubastove]

If it was always serviced be Dinan,did the guy have any internal mods ,cams etc. ?

Sorry, not always serviced at Dinan. But most recent service records from the past 4 or so years. Before that were a couple of other German auto garages, and BMW.

Previous owner was not a car guy, he didn't know what the subframe meant when I asked if it was reinforced. I'm fairly certain this car is 100% stock.

[Arith2]

I got anywhere from 7mpg to 23mpg. I liked to speed, but not around other people so I did alot of slowing down. A BBK would actually benefit my on the street. I experienced brake fade quite a bit bringing my car down from 140 or so.

If you literally did all the maintenance and it was well done, I'd start looking at wave forms. Something is causing the fuel trims. Everything always has an answer, it's just matter of finding it. The problem is you will need someone's $5000-$10000 Oscilloscope.

[mrgizmo04]

BBK would actually benefit my on the street. I experienced brake fade quite a bit bringing my car down from 140 or so.

Doogan, is that you?

[Ceelooboob]

I average around 22-23 mpg on my 04 M3, that is mostly highway driving.

[dr_011]

18/24 typically in my '05. Best I ever saw was 31 MPG in 6th gear at about 80 mph IIRC.

[Arith2]

Doogan, is that you?

Sorry to disappoint but I'm no Doogan.

[terra]

Average 22-23. Can squeeze 30mpg on the highway if I really try, more typical for me is 25-27.