I have a 91 f150 4x4 with a 5.0. I bought the truck for 450 so I knew it was going to need work no big deal... My problem now is I'm only getting 9 to 10mpg. I have done a complete tune up as far as plugs wires msd dist cap and button and msd coil. New egr valve, idle air control valve , and still not any better so I figured cause the exhaust was missing almost everything went and put a magnaflow muffler on for temp till can afford headers and duals... Still nothing better fuel milage wise any ideas thinking maybe o2s next after that out of ideas..

 

And what's the best way to get rid of the smog pump and all its garbage my 96 already had it all taken off when I got it and ran great actually just had the pump there and no hoses going to it...got an average of 17mpg out of it and it was lifted with 38.5s..the 91 is still stock!!

 

Is that 9-10 mixed/average? I would expect it to be right in that range, so what are you looking for? My 06 5.4 barely gets 12 in mixed driving, and it's 15 years newer. Unless you accounted for and changed the speedo for those 38.5s, that mpg will be wildly inaccurate.

Rear end ratio? Mileage on it?

 

I would think 9-10 is a bit on the bad side. If everything is right you should be able to get 14. my 99 gets 14 combined usually.. its a completely different engine though only the mass of it is the same.

 

Gear ratio is stock not sure what that is tho. Only has 130k. Looking to get at least 15. Most of my driving is four lane by pass driving at 65mph cruising.just drives me nuts watching the fuel gauge go from full to three quarters in 20 miles