Average Gas Mileage?

[Threehz]

Well I did a lot of searching and I could not seem to find any threads on this, just a few random ones about people getting really bad gas mileage problems.

I want to know what people are getting as average gas mileage figures. Obviously this will be skewed by many factors, biggest being chassis of course. So it'd be best if you state your car, MPG, and any important mods or as many as you want to list.

I just bought my 91' 318is, haven't been able to collect to many figures yet but will keep updating.

First time, pretty hard city driving, 21 mpg. (also had a flat)

Second run, new sparks and air filter, 23 mpg. (shit tires)

I have just gone from polyurethane motor mounts to stock which has made a pretty big difference, also changed oil, oil filter, fuel filter, so we'll see how that effects things in this next run.

Mod wise, mustang injectors, mess under hood removed, eibach lowerings in front, IE springs in back, KYB gas adjusts in back, bilstein sports in front, other then that the tires on are currently shit but hopefully I'll be getting new ones this week. Also pulls to right which I plan on straightening out soon, but that's also effecting mileage a little.

I'll throw a poll in even though it won't be very informative without details on car specs so posts are preferred.

[DesktopDave]

My 286k mile e30 sedan's lifetime average is 29.61 US MPG.  I average 25 city/31 highway.  My driving is about 2/3rds highway.  My Garmin estimates 41mph driving average, so I'm no speed demon.  I also take mass transit to work so there are virtually zero gridlock hours on the car.

Mods include full synthetic lubes (10w40/ATF/75w90), Coolant is 66% distilled water.  New O2 sensor, hose delete mod, 19# injectors, COP and 3.73 diff.  Stock air filter & box.  Stock 14" rims with generic all season tires @35psi or so.

I now keep very detailed records for cars.   It's too easy to get out of control on spending if I don't.   If anyone wants a copy of my Excel worksheet to track cash flows let me know...

I ran a few new formulae through, here's some fun mileage results:
Best octane: 93 octane, 31.1mpg (averaged over 14793 miles)
City or highway? Neither...I must drive too fast...mixed driving gets me 35.1mpg (averaged over 2373 miles)
Best season: Fall, 31.7mpg (averaged over 6034 miles)
Best fuel: Exxon 93, 30.3mpg (6679 miles)
Best year: 2011, 31.5mpg (7867 miles)

Worst:
Discount grocery store fuel >10% alcohol averaged 28.1mpg (1940 mile avg.)
Urban driving only did 25.1mpg (3729 miles)
Spring driving got me 29.3mpg (5040 miles)
2010 averaged 29.4mpg

[deansweet]

Similar with Dave here.
My 344k mile e30 gets just about 28mpg with our current city/highway driving habits.
Absolutely no mods to motor/suspension.
I run Shell's premium 93 fuel.

[Threehz]

Beautiful layout Dave, I keep a similar spreadsheet of everything that happens to my car down to the last detail and what's changed.

I just got 22MPG with city driving, however yesterday went on a 300 mile or so trip and looks like it'll come out somewhere around 30-32 with mixed highway and city. We'll see later today!

Once I get all my little issues sorted out hopefully my fuel consumption will rise at least a little.

[DesktopDave]

Thanks!  I've gained >3mpg over my ownership...not too bad, all-in-all.  In addition, I've been using it for work, so they more or less pay the bills with mileage reimbursement!

Sliced the data up once again...by mod this time.  I missed a bit of data (forgot to note the COP install date) but it seems that the biggest bang for the buck was the hose mod.  Killing vac leaks is important!

Baseline:
29.2 mpg over 2208 miles (14" rims, 3.73 diff, thick synthetics)
29.8 mpg over 6066 miles (summer tires, summer fuel mix)
30.8 mpg over 3848 miles (thinner synthetic oils, P/S delete)
30.5 mpg over 3187 miles (winter fuel, new O2 & NGK twin electrode plugs)
32.9 mpg over 3222 miles (hose delete, 4-hole 19# injectors)
28.3 mpg over 214 miles (thicker motor oil)

The thicker oil (10w40 Mobil1 "High Mileage") hasn't been running long enough for accurate numbers.  I'm pessimistic so far (28.3 mpg) but it's a compromise.  I'm seeing uncomfortably high levels of wear metals than I'm comfortable with running 0w20.  Burning out a motor in 20k miles to gain 2mpg isn't very economical!

[Dhohn]

I seem to average about 36 on the highway and about 25-26 in town.

Stock motor and car with open 4.10 gears
136k

[Threehz]

Ok so did just under 300 miles, almost half and half city and highway and it came out to 29.9mpg, pre-trip I added a bottle of Lucas fuel system cleaner with my fill up, we'll see how that affects my normal city driving mileage, however I also have bigger tires on now which may affect things as well.

I have yet to sort out my idle Lambda 1 code so that might be causing an issue (however I haven't seen the engine light come on at all since the trip, today will be the test)

[victor.askew]

I filled up today and after a new cylinder head installation, water pump, air filter, fuel filter, 02 sensor, plugs,wires, 2 ing coils, cleaning the ICV and the MAF sensor ect it came in at 25.7 mpg. I drive up and down hwy 9 and hwy 17 everyday plus the stop and go of city driving in sunnyvale, mt view, palo alto so I guess this isnt to bad. I tend to have a heavy foot also.