This topic has been discussed many times.

Basically, it breaks down like this:

Things that make your gas mileage go up:
-Engine is tuned and timed properly
-Stock Cam
-Electronic Fuel Injection
-Free-er flowing heads (E12 head and/or porting/polishing)
-Upgraded Exhaust
-Electronic Ignition
-Digitally Controlled Ignition (EDIS setup with Megasquirt or Megajolt)
-Overdrive Transmission upgrade
-More Freeway Driving/Less Stop and Go
-A Light Right Foot/Not Drag-racing the high-schooler next to you at every light.

Things that make gas mileage go down:
-Bigger Cams
-A Weber 38/38 or DCOEs
-Poor tuning/timing
-Emission Controls
-Heavy Right Foot

Mileage will range from 12 for a poorly tuned crap box with the wrong carb/engine setup to upper 20s with EFI and an overdrive trasmission. There are stories of some getting over 30. Once I get my EFI going, I'm setting my goal at 35 hwy MPG.

Good luck!
_________________
ClayW
1976 Fjord 2002 Sunroof

Project Blog

"Finish the thing, do it right the first time and drive the son of a bitch!"
-Gray Baskerville on hot rod advice

This topic is beating a dead horse. The original poster should at least make the effort of searching the archives, if not the net, before asking such a broad question.

....and of course your MPG will be more or less depending
on climate, state of tune, right-foot behavior, and other
stupid things


_________________
1976 BMW 2002 #2743711(sorry I sold it 12/25/06)
1986 BMW R65 650cc twin 19k miles
1964 BMW R27 250cc single 15K miles
2002 BMW 325xiTouring 29k miles
1984 MERCEDES-BENZ W123 300D Turbodiesel-188k miles fein-DIESEL

psyran wrote:

What is the average miles per gallon I can expect to attain on my 2002? Am having it completed in about a month. Wondering if I maight want to use as a daily driver. Thanks

between 15 and 30.
Drive 10 tanks and average it out!
Why should we do your work?
_________________
75 2002

Crap in your trunk or fat passengers can impact your mileage as well.
I justify carrying all the crap in my trunk by having skinny passengers.
No. I didn't figure the fat driver (me) into the equation.

Also, tire inflation and roof racks are two big mileage killers.
_________________
Steve J
72 tii / 88 M3 / 99 328 / 08 MCS R55
& too many bikes

It doesn't help that we're driving the aerodynamic equivalent of a large brick, that's for sure!
_________________
'74 2002 (undergoing Megasquirt conversion!)

Its not what you drive but how you drive!

Jeremy Clarckson drives an M3 against a Prius.

I know this is far from the definitive answer but it does illustrate (kind of) a very good point.