I just bought a 1991 4WD F150 with 117,000 miles on a 351 engine, drove it home on the highway, and averaged 10 mpg at 65 to 70 mph. Now that I am driving it in town, I average 5 mpg. The engine starts and runs terrific, and has mad power. Pulled the plugs, and it looks like the engine is burning LEAN. The transmission shifts well, overdrive works, and transfer case shifts smoothly between 4wd, 2wd, high and low ranges. I put in a new air filter, and changed oil and filter, using Mobil 1 synthetic. Is this typical 351 mileage (which is worse than big block Chevys I've owned) or do you have any idea what might be wrong? I'm perplexed.
Thanks,
Rockwell
Thanks,
Rockwell
Mar 15, 2006 at 11:56 AM