Avgd 33 mpg on my 325i

[///M42 sport]

I just got done with a 600 mile trip and averaged about 33 mpg (according to my OBC). I thought this was pretty awesome considering I have a 325i cabrio with 4.10 diff. I run redline tranny/diff fluid and mobile 1 synthetic engine oil. Also I was going about 60 the whole way :)

[TDE30]

Wow. I wonder how accurate the OBC is. I know that we've had issues with the accuracy of the OBC IV in my father's M5. Very impressive though, especially with a 4.10.

[Turf1600]

When mine says 33 it's usually around 30.

[E30ownerwithanopinion]

stock wheels on the car?

[///M42 sport]

Yeah stock wheels pumped to 34 psi front and 38 psi rear. I had my hardtop on and it was loaded to the brim with all my shit too. I'll have to post pics later.

[Nihilator]

My OBC consistently reads 10% too low. But by calculations, I usually average 27.5 mpg in mostly-highway miles, at about 67 mph.

The hardtop helps...it produces a bit less drag than the soft top. And 60mph certainly helps.

--Chris

[OrganicMechanic]

I thought that a 2.93:1 rear diff would boost my MPG...nope worse by about 5 mpg, I am thinking that it put the engine out of the powerband and tit wold have to really work hard to get back to the torque peak, whereas the 4.10 puts the motor in powerband and needs less gas to maintain monentium. I think a 3.73 is the best for MPG, of course I like acceleration. Now I am babbling. Best I ever got was 31 and was coasting a lot.

[Bimmerista]

Back in Dallas??

[Jon325i]

I have to question the numbers your OBC is giving you. Instead, calculate the total amount of fuel used divided by the number of miles driven. During the early part of this year I had to de-tune my E30 some since the job I've been doing requires a lot of driving (and I've been documenting every mile and every trip to the fuel pump for next years' income tax purposes). Here's a breakdown of my set up....

Car: 1991 325i, 2 door, 5 speed
Odometer: 200,141 (as of 8/1/08 )
Motor: completely stock including stock chip
Differential: 3.73 limited slip
Wheels: 15x7 Racing Dynamics
Tires: 225/50 Falken Ziex
Tire Pressures: 34psi at all corners
Suspension: B-Sports, IE Stage 3 springs, stock sways, no camber plates
Full interior, A/C, spare tire, etc. but nothing else in my car (I'm a neat freak)

Average fuel economy (mixed): 26.1 mpg
Average highway: 27.8 mpg
Average city: 24.0 mpg
Calculated total miles from 16 gallon tank: approx. 410 with a small reserve

With the increase in fuel prices, I've made some adjustments to my driving style to maximize my fuel economy. I typically drive 65-70 and the freeway and keeping things sedate when on surface streets. Also using 87 octane fuel exclusively.

Jon

[allwheeldrive]

Car: 1991 325i, 2 door, 5 speed
Odometer: 200,141 (as of 8/1/08 )
Motor: completely stock including stock chip
Differential: 3.73 limited slip
Wheels: 15x7 Racing Dynamics
Tires: 225/50 Falken Ziex
Tire Pressures: 34psi at all corners
Suspension: B-Sports, IE Stage 3 springs, stock sways, no camber plates
Full interior, A/C, spare tire, etc. but nothing else in my car (I'm a neat freak)

Average fuel economy (mixed): 26.1 mpg
Average highway: 27.8 mpg
Average city: 24.0 mpg
Calculated total miles from 16 gallon tank: approx. 410 with a small reserve

I'm almost the exact same setup as you. And my mileage is damn near spot on.

[///M42 sport]

Back in Dallas??

Yep

Granted my calculations weren't precise. But I did notice my OBC reading went down to 28mpg when I sped up to 65. So I was reving at 3k instead of 2.5k (when cruising at 60) If I do another road trip, I'll come up with more precise numbers.

[Wishno87]

My dad got around the same on a trip a few weeks ago. He has a 92 cab with 86K on the odo.

[92 mtechnic cabrio]

I fill up on average 14 gallons per gas station visit. On those 14 gallons, my car drives 400-430 miles.