Hey...

I'm getting very bad gas mileage out of my 5.0 in my 94 F150. I always just figured it was my 33's, but I've had a set of 31's on there for a week now. So far my best tank got me almost 12mpg! Its a 5.0, auto, 3.55 gears, with 60k miles on it. Its got a bunch of new junk like plugs, wires, ect... and fresh Mobil 1 oil and even at 55-60mph I can't get over 12 mpg! I'm started to get here.

My main question here is this. I am running shorty headers, stock collector and cat, then straight pipe back. Is this killing my gas mileage. This is the only mods I've done to the truck that are engine related. When I first got the truck I was able to get 20mpg on the highway if I took it easy. The only mods I had then was just the straight pipe after the cat. Could I have gotten rid of to much back presure?

What else could cause such poor gas mileage?

 

Has the o2 sensor ever been replaced? Even if the CEL isn't on and the sensor is still working it's performance could be degraded. Replacing the sensor can sometimes give you up to 5mpg and 15 hp. It might be worth a try if it's not too expensive.


-Jon

 

60k miles and still the original O2 sensor. Couldn't hurt to give that a try. Thanks...