Ok, the car's an 88 Iroc. So far all that I know is done to the car is a flowmaster muffler, k+n's, airfoil,accell, msd 6a, and a 3.70 posi. (9-bolt) The thing gets about 18-20 mpg highway and it's killing me.
What can I do to the motor to bring it up into the 20's???? This sucks!

------------------
1980 Camaro, '88 Police 350 engine, Headers, full exhaust, completely redone, my baby!
1988 Iroc-Z L98, MSD 6a, Accel coil, K+N's, Airfoil, Coolant Bypass, Flowmaster, Gears, Late model Bose, I like the 80 better

 

Ditch the 3.70 and go to a 3.23. The higher RPM's on the interstate are not helping your gas mileage at all. My '90 with the 3.23 gets 24MPG at 80-90MPH in overdrive all day, but I doubt it gets up like yours. Ahhh, everything's a compromise .

 

Believe it or not nobody around here has a 3.27 or anything close, usually just 2.77's - and i have a feeling i'd cry if i had a 2.77. I'm kinda looking to get the mileage up with the 3.70's
Or if anyone here wants to give me their 3.27 and some cash, feel free :-)

------------------
1980 Camaro, '88 Police 350 engine, Headers, full exhaust, completely redone, my baby!
1988 Iroc-Z L98, MSD 6a, Accel coil, K+N's, Airfoil, Coolant Bypass, Flowmaster, Gears, Late model Bose, I like the 80 better

 

The BW 9-bolt came stock with a 3.23 ratio, but if you're determined to keep the gears, about the best you can do is a full tune-up, synthetic fluids and maybe some PROM calibration to make it run leaner. Make sure you don't forget the oxygen sensor. In fact, replace that first if you don't know when it was last replaced since that could be your problem. You may see 23-24 with that and a full tune-up if you keep the speed down on the interstate. Hope this helps.

 

I have a 91 z28 350 with 73,000 miles on it. The motor runs great and it only gets about 13-14 mpg and about 17 on the highway. All the mods the car has are a k&n and flowmaster exhaust. Be happy : ) with what you got.

 

I would, but I've seen guys getting high 20's with those cars. And it's also a kick in the *** when my '80 Camaro with a 2.73 and a 3-speed gets like 17 overall and as much as 22 on the highway, with a Carter AFB!

------------------
1980 Camaro, '88 Police 350 engine, Headers, full exhaust, completely redone, my baby!
1988 Iroc-Z L98, MSD 6a, Accel coil, K+N's, Airfoil, Coolant Bypass, Flowmaster, Gears, Late model Bose, I like the 80 better

 

Change the 02 sensor if you haven't. I changed mine and it gave me 5mpg easily. My other one wasn't throwing any codes either.

Steve

------------------
89 GTA G92
305 TPI WC 5spd w/3.45
Accel Cap & 8mm Taylor's
Custom 4" Cold Air Induction
Jet Airfoil
K&N Airfilter
160 deg stat/fan switch TB Bypass - Steel Rad
Cat back 3" Exhaust w/Terminator Muff.
HiGh FlOw Dynomax Cat
Spohn LCA's - KYB GR-2's
Moroso Crank Bolt and roller pilot bearing.
Autometer Vac+Oil Temp