I bought a 1990 -150 with an injected 302 in September. Its a flat bed with an Approx 5" body lift on the cab. 31.5X10.5x15 tires. When I got it there was no question it ran bad and I got about 10 MPG. After a few months I tore into it and found why it was missing, Burned exhaust valve which inturn cracked the head. 2 new heads later, I still get 10 MPG runnin around, 12 highway. Whats normal for a 302 like this? Seems low to me. What work can a guy do to a 302 to improve mileage?

 

First off how are you determining milage? It should do 15 around town and even better on the hwy.
It's EFI right? What tranny?
Is the O2 sensor present and electrically connected?
Dual or single tank?
What is fuel pressure?
Any signs of fuel in the vacuum line from the FPR?
Any codes present?

 

First thing I noticed when you started your list was tire size, they are taller than the p235/ 70R/15 tires that should be on it, so what I am saying is just this, the mileage will be off and your fuel mileage will be as well!

 

The 5" body lift is going to kill your mpgs....

those tires aren't that much bigger than stock though so it probably wouldn't be off by too much i would assume....

Mine is lucky to get 14 on the highway, but it runs like cow manure.

what is the flatbed made of? wood? diamond plate? more weight=less mpgs. I would still think you'd be getting slightly better than that tho..

 

Don't know your trans or if 4x2 or 4x4, but read it and weep:

http://www.fueleconomy.gov/feg/sbs.htm

1990 302, 3 speed auto, 4x4 EPA rates 11/12.

4 speed auto: 12/16

5 speed manual 11/15

4x2:

3 speed auto: 12/14

4 speed auto: 12/17

5 speed manual: 13/17

YMMV

 

I agree with the others.A different size tire than factory will throw off the speedo.

My stock 91 regular cab,long bed,4X4,5.0L, gets about 16-17MPG.


and...........................Welcome to the site.

 

4x4 - 4sp auto - I havent looked into the other suggestions. It does have an o2 but i noticed just yesterday that there is an exhaust leak just up stream from it - how bad will this throw things off?

 

Any exhaust leak upstream of the O2 will affect milage so check that out, inspect the tube that connects the heads across the back of the motor this rusts out or cracks and will sound like a manifold leak. You should also check the other things mentioned as they could all contribute to the problem.