MPG indicator on the M3 lies

[deepsea]

Yeah the factory lie-o-meter does just that, lie. Everyone of them is skewed to read a little on the plus side. Its not that car makers cant figure out the math, its that they want it that way. Hand calc. is the only way to go. I average 16mpg with a mix of city and hwy miles. Best tank so far 19mpg all hwy at 77mph cruise control. Worst 14mpg. I used to own a tuned diesel truck making 450 HP and 800 FT/LBS Tq. 6.4 L , best mileage in that was 14.2mpg. Wost 10.6mpg so the way I see it 16 aint bad at all!

[fuddman]

Computer currently shows 21.3. It's been as high as 21.5.
About 7700 miles on the car. Not much stop and go driving.
Do not like the low-on-gas warning coming on at quarter tank.
Love this thing!

[tico1028]

Mine has been showing 99.9 MPG for a few weeks now. BEAT THAT! No but honestly, anyone know a way to fix it? lol.

[rdollie]

Keep in mind that ethanol blends lower your fuel economy (too bad it doesn't lower your fuel bill!)

I drive with a pretty heavy foot and get the same 16.x miles per gallon with the M that had with my wife's XC90 V8, my Superduty diesel pickup I just sold, the S60R 6MT I used to own and track on occasions, the old Ford Taurus I always rented from Hertz on business trips years past, etc. Not sure why but I tend to drive everything with a heavy foot and I always average out to 16.x miles per gallon (except in our boat of course!)

I had an Infiniti G37X rental last week and got the same magical number (of course I thrased that engine quite a bit - lovely motor.) The only recent exception has been a couple of recent hybrids that averaged in the low to mid 20s.

Regardless, I'm not complaining. If I wanted better fuel economy I wouldn't have bought a car that begs to be driven hard.

[besiktas]

I dont think anyone really complains about the mpg, most people complain about the size of the tank. it would be nice to have a 100 litre (26.5 US gallons) tank instead of the 65 litre. A 3.35 in US or for instance another engine 3.20 in europe they all have the same size gas tank size but they are much more fuel efficient, so they dont have to refill evey 5 days.

[Mr. ///M3 RD]

Originally Posted by Superfly_M3

Hello,

So I've observed an average indicated MPG of 14.2L/100km - 16.5 US MPG (I've reset after each refill for a couple of tanks) and then I hand calculated my consumption to be 16.5L/100km - 14.3 US MPG

IMO the variation is huge. Anyone else experience this?

I find driving in the city and keeping track of the fuel consumption quite useless. I do however compare the computer feedback with actual bill quantity and milage driven for long road trips and both agree within a few percentage points.

In general I am not concerned about this issue at all if I was then I would not be driving a ///M3.

Fuel consumption on our cars all depends on how we drive as we all know.

[checkmate]

My DD mpg is 16.9mpg.

[Motif]

Originally Posted by deepsea

I used to own a tuned diesel truck making 450 HP and 800 FT/LBS Tq. 6.4 L , best mileage in that was 14.2mpg. Wost 10.6mpg so the way I see it 16 aint bad at all!

What tuner did you use that you got that low of numbers? I use a 210 tune from Spartan and ended up with 480 with 909 ft/lbs tq.

[deepsea]

Originally Posted by Motif

What tuner did you use that you got that low of numbers? I use a 210 tune from Spartan and ended up with 480 with 909 ft/lbs tq.

I had a custom tune from River City Diesel. The 450 tune with a DOC, DPF delete pipe, S&B intake, 20" wheels with 35 BFG's, and a heavy right foot. All that torque was really fun but I have to say I like my M3 much better!

[deepsea]

Edit: the 10.6mpg was stock with DPF and DOC intact.

[Motif]

Originally Posted by deepsea

I had a custom tune from River City Diesel. The 450 tune with a DOC, DPF delete pipe, S&B intake, 20" wheels with 35 BFG's, and a heavy right foot. All that torque was really fun but I have to say I like my M3 much better!

RCD tunes are clean from what i hear. 20s w/35s are not horsepower/MPG friendly. 6.4s are surely fun and are stupid easy to tune ( not easy to work though ) but i am heading toward M3 or a 5 ASAP upon my return to US

[TVMA Doc]

Originally Posted by Superfly_M3

Hello,

So I've observed an average indicated MPG of 14.2L/100km - 16.5 US MPG (I've reset after each refill for a couple of tanks) and then I hand calculated my consumption to be 16.5L/100km - 14.3 US MPG

IMO the variation is huge. Anyone else experience this?

My computer states that I'm averaging 15.4 MPG. Calculating based upon gallons used/miles driven, I'm averaging 16.7 MPG.

[Superfly_M3]

Originally Posted by the-moss

Yeah most gas around here has 10% ethanol. All 93oct though.

I have never hand calculated it, but I'm pretty sure I get 230-250 miles before I feel I have to fill up.

I'll hand calculate it for a few tanks once I get her out in the spring.

Even at 250miles/tank works out to 15mpg ... not 20

[Superfly_M3]

I'm not complaining about the gas mileage. I'm complaning about the accuracy of the MPG computer