I have a 1993 F-150 4.9L. It has 125,000 miles on it. It does not smoke or backfire. It runs great, no complaints there, but the gas consumption is terrible. I am getting about 12 Mi on the highway! I changed the plugs, air cleaner, sprayed the throttle body with cleaner, ran 2 bottles of B-12 thru the tank, changed the fuel filter, changed the oil. I sacrificed two virgins (Tough to find...) and I still am getting bad mileage. The intown mileage is worse! The only thing I can notice is a higher than normal idle RPM in park but not by much... Maybe a couple 100 over normal. I looked around at the vacuum hoses and they are old looking but none missing.. HELP.... I need to purchase stock in Sunoco if this keeps up.

Sincerely,
Gas Guzzler! A.K.A Justin


Justin Grant

 

What is the gear ratio of your differential?

If you have a low ratio which is good for towing and hauling, your highway mpg will suffer.

On my 96 4.9L my ratio is 2.73 which is very high. Its good for highway driving but it wont hardly tow anythin.

If you don't know your ratio, get a flashlight and crawl under the differential and look for a small metal tag bolted onto the differential. Stamped on this tag is the gear ratio.

Really I've been thinking of getting mine changed to a lower ratio.

 

I have a '92 with that engine and a 3.09 rear end. I get 11 mpg hwy. You get used to it Of course my check engine light is on, i think it is the o2 sensor, if i fix that it should be better.

-Jon

 

WOW!! I'm not worried about my mileage now. I get 16 mpg city and 18-19 hwy. With a 5.0 and 3.55LS.

------------------
'96 F-150 302
Hedman Hedders, Catco Cat., Gibson Super Truck, K&N F.I.P.K.

 

I have a 308 rear. My V8 5.7L car gets better gas mileage. There has got to be something I can do to get better gas mileage..

Thanks!

 

Have you cleaned the Throttle Body and IdleAirBypass Valve. Check spark plugs, wires Cap and rotor. Check the coil(MSD TFI coils work great). Check/replace the O2 sensor. Check for any stored trouble codes. Are you running stock tires (235's)? If you are running bigger tires eg 31's your odometer will be off by .07. If you are running 33's it would be off by .14. In either case multiply the indicated miles traveled by 1.07(in the case of 31's) and you have a better figure for caculating.

WHaynes
93 F150 4.9L 4x4
4" ProComp StII Lift
BFG 33in 4.10's
Detroit TrueTrac's

 

I have a 92 302 that was get 11 miles to a gallon. I just up grade my ignition to MSD
I put in a MSD 6A control box, MSD Ford TFI coil MSD 8.5mm Super conductor and Accell Rotor and cap. My milage went from a average of 11.3 to 15.8. The truck runs so much smoother and has alot better pick up. The total cost for the up grade was around $240.00. I bought them at summit racing.
Also they have a wire harness kit to make a very easy install. Hope this helps

 

I had your EXACT problem. The clue is the higher idle rpm. I had a major vacuum leak. Drove it for 2 years not knowing what was wrong, but had terrible mileage (two tanks a week). Finally it broke down- I thought the engine blew it sounded so bad. Turned out to be a blown intake manifold gasket ( very common). There's an upper gasket and a lower. Hopefully it's the upper if that's what's wrong with yours. The lower is more expensive to repair. Get a flashlight and look around the manifold seam for a piece of the gasket hanging out. Also try re-torquing the bolts. When I replaced the gasket my mileage improved to one tank a week. Good luck.

 

I'm still averaging 15mpg, in town with the A/C always running.

Not bad for 90k miles.