hey new to this website. Now i know ford does not have the best MPG on there trucks but however i own a 1991 F-150 with the 5.8l with dualexhaust and a K and N air filter.all im using is the front tank 14 gal.and only getting about 120km per tank.Does any one else get this bad of milage.New champion plugs,fuel filter, and just used fuel injector cleaner.Is it out of time or what else would give it bad milage like that.Would a throttle bottle spacer help the MPG.

 

Something isvery wrong with your truck. A 95F250HD 5.8L 2WD Auto OD 4.10 gears we have at work almost always gets 200 mi ( 320km) per tank, occasionally squeezingup to 450 mileson twin tanks. I assume that 14 gallons is what you typically add when filling it, because actualtank size is usually between 18 and 19 gallons (not sure if short bed is smaller).

My 86 F150 5.0L 4WD Auto OD 3.55 gears got better gas mileage in its youth. It even got 15 mpg fully loaded towing a loaded67 Ranchero on a dolly when my parents moved. But there were times as it got olderthat it sucked gas. Maybe it was the 31" mud tires, or that it sucked raw fuel through a vacuum hose when fuel pressure regulator diaphram failed, later leading to weird EGR noises and plugged cats. Or for years it would gasp if I tried to go over 3000 rpm due to a problem with the valve between the twin tanks. But I had none of those problems with the 95.

 

thanks for the reply i should have mention that i have the vacume line pluged off the egr valve. would that make it harder on fuel. I unplugged because in the cold mornings it would act like it was flooding and running realy rich unpluging that vacum line did help but not very much. not sure what to do.