Hey guys I was wondering if I could get a quick reply from as many people as possible on what kind of fuel economy their car gets on the highway. Also if possible could you also list the mods done to the car? I am trying to figure out where I am starting from as the car I am currently working on has never been running long enough to take it on the highway since I've owned it. (hence the reason I'm pulling the whole thing apart and starting fresh.)

 

I've got a stock (no mods) '88 IROC with a 5.7 TPI with 106,000 miles on it and get just over 18 miles to the gallon driving mostly on the freeway around Phoenix.

 

Stock, high miles 350 TPI in my '92 Formula, and I see 20mpg in my highway commuting to work.

 

20MPG on highway with no overdrive. Modded carbed 350 here with 3.23 gears. This question is asked really frequently, did you do a search? You'll get a schwack more results than waiting for people to reply... Just a thought.

 

I get about 15/20 in my 86 Camaro with 305 TPI. It depends on how you drive your car really.

 

I did try to do a quick search for this, but alot of people were posting things like: "yea I get 15-18 in my car", but I was looking for a little more detail like, what size engine, mods, gears, tranny(auto or man). Things like that. If this has already been posted before, I apologize in advance.

 

2.8L auto
TB heater bypassed
"****-warm" air intake - i.e. K&N near the old air filter location, which is quite open to the outside, yet still in the engine compartment. 3" PVC used for most of the intake.
180* stat.

Almost all highway driving these days - 250 miles to the tank almost exactly every time. FIll ups about 13.5 gallons, so 18.5mpg.

I drive like a banshee.

 

dead stock 350 92 TPI with true dual exhaust with manifolds, 2.42 & a 700.
depending on how i drive, 15~18 city with the A/C on
hiway is just over 25 with A/C on & running around 70+ MPH.

 

1989 IROC-Z with 5.7 TPI about 34,000 miles on remanufactured motor, has 52mm throttle body, Holley 24lb injectors, slp runners, stock exhaust manifolds with Catco hi-flow converter and Borla cat back exhaust. 342 gears in the 10 bolt posi-rear (which hurts mileage) About 15MPG highway.

 

1991 Formula with a high milage 305. Mildly ported heads, eldebrock 3704 intake 350 tbi, bosch +4 plugs, tuned ecm, and a tbi 350 truck cam (cheap build). 700r4 with a shift kit.... stock stall.

with 2.73 gears 17-19 city and 26-27 highway (70-75)
with 3.42 gears 16-19 city and 22-24 highway (65-70)

The best milage will always be had if you can set your cruising speed to the engine rpm's. If you make peak torque at 3,000 rpm's than that will be where best milage is in theory, but theory doesn't always work.

For better milage, you can always try a shorter duration cam, shorter stroke, longer rods, rollers(cam and rockers), retarding timing about 2-3 degrees, lower than stock stall converter, and numerous other options. It may be best for you to experiment some with the car.

 

When my car was running nicely, I got about 150 miles on between 1 half and 2 thirds of a tank or so.

 

89 GTA L98, automatic with 3.27's. Around 28,000 miles on the odometer.

Mods are your basic intake and exhaust bits. Mileage is 15 mpg in the city. 21-23 on the highway. I have the small gas tank, so computing a tankful in miles is useless.