I have a 1980 F100 with the 4.9-liter six-cylinder engine (one-barrel carburetor) and automatic transmission. It runs great, but gets only 11 miles per gallon, even in highway driving. Is this typical? I'd appreciate hearing any thoughts or suggestions.

Thanks!

 

Check the carb. They have a tendency to blow the accelerator pump, and or the base loosens up from the bowl. My best advice is to rebuild the carb, check vacuum leaks(especially the intake to cylinder head gasket). Also verify ignition timing(8 degrees BTDC). Check the plugs. I had an 86 that when it started to lose mileage, it was time for plugs. Hope this helps some.

Robbie

 

Be careful if you go to replace this one... the nautre of the project makes it pretty dificult if the engine's gonna stay in the engine bay.

 

What gears does your truck have, and what size tires are you running?

SL

 

The tires are stock 15-inch. I have no idea about the rear-end gears, but I doubt that anybody ever changed them out. It's certainly never been hot-rodded.

 

I would hook up a vacuum gauge so you can monitor it from inside the cab. If you get low readings most of the time, especially at cruise speed, you may have a clogged converter or muffler. Do a compression check as well. When was the last time it a COMPLETE tune up?

SL