I may be getting a '91 5.0 SuperCab in the very near future, and need some . The truck will be my daily driver (short-term, hopefully) but it's main purpose its to pull our travel trailer. What mods will maximize the MPG potential of this truck? FWIW, it has an automatic tranny. As always $$$ is somewhat limited. A tune-up kit is a given (plugs, cap, rotor, wires...saw an nice Accel kit in Summit). I was thinking of 1) a MAF conversion or 2) for similar $$$ keep the speed density, and do an FIPK, 3" cat, 3" si/so cat-back system, and *MAYBE* shorty headers. I don't want the truck to be too loud. The mellower the better, as it'll see highway cruising mostly. I just want to improve efficiency as much as possible, to maximize the MPG. Thanks for any opinions.

 

And the rear end ratio is???
That is the single most important determinant of mileage.

 

Careful with the exhaust, an exhaust system with low backpressure will increase higher rpm horsepower but it reduces low end torque which will cause a decrease in gas milage, especially when towing.

-Jon

 

I'll have to get back to you eventually on the rearend gearing, as I have no clue, and the truck is not here where I can get numbers off of it. If it matters at all the truck is an XLT Lariat model, were they the most common?

 

I was getting 8mpg out of my '96 302 4x4 for a while, before I made the following mods for performance reasons:
K&N intake
Flowmaster si/do
Hypertech CPU tuner
The performance increase was well worth it, but the mileage increased to 10mpg which was really sweet! 2mpg sounds like no biggie, but that's 25% better than 8mpg! It was still lacking low end grunt, with the 33" tires killing the gear ratio, so I recently replaced the diff's with 4:10's and an Eaton Limited Slip pack in the rear. I've been smiling ear to ear since. No stable MPG numbers to report yet, since I haven't driven it NORMALLY for 2 full tanks yet since then. Will follow up soon.