When you increase horse power does it always increase gas mileage? If not, in what instances then? Anyone have any suggestions for a good starting point with an 89 f150? I'm thinking cold air intake; new fuel injectors, intake manifold, supercharger...

 

Increasing horsepower usually means decrease in fuel mileage. Rarely does it get better. Yes sometimes hp gains increases fuel mileage but rarely mostly with new cars changing the fuel mapping but not on older cars. To make horsepower you need more bang more bang means more fuel. Nitro funny have lots of horsepower but dont get 100mpg.

 

Welcome to the F150 Forum

 

Well my understanding was that when you add more horse power it is usually a more efficient engine and if your driving around town under normal conditions not racing and stomping the gas your engine is running more efficiently ie more mpg and when you stomp the gas that is when your using the extra horse power and burning more fuel