I know this is a REALLY broad question but what are the factors that dtermine your cars mileage?

Just how heavy of a foot you have.

Yup, that is the biggest variable I find.

Other factors like the overall condition of the motor and critical parts, it's state of tune, having your tire properly inflated, how optimal your computer programming is, and properly operating sensors all affect gas mileage.

The reason I asked is because I am on planning a 383 Mini-Ram and I know I should not be worrying abou mileage with that combo but The engine is gonna be powerful regardless I just wanted to know what engines components i would have to choose to maximize fuel effeciency btw I am planning on a 9:1 comp. ratio cause it's gonna be supercharged I am also going to use alum vette heads, a t-56 and 3.73 gears any help would be appreciated

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This ain't perfect but here goes.
#1 the amount of fuel in each cylinder when fired.
#2 the amount of air in there
#3 the rpms
#4 the gearing of the car.


*Note this is just my opinion*

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91 z-28 305 700R4
3.73 gears out back
T-Tops and Black all over.

You're building a high horsepower engine, a 383 at that, and your first priority is gas mileage ?!? Something's definetly wrong with THAT picture buddy! LOL



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1991 Z28

383's are demons of a motor anyway so I figured i'd build it on the conservative side ,the reason i went a 383 is it's easier to make power wthout alot of extra money so if i dont max it out ith a big cam,big headers, and al the other things to squeeze power out of it i shouldn' do to bad on mieage

the bigger the displacement, the more fuel needed. the more fuel needed, the less your MPG will be. that, gears, and your right foot are the biggest factors.

Like the first guy said how you drive is a big factor. Aerodynamics is another. Engine displacement isn't that big a factor although smaller engines usually have less internal friction. You have to keep your engine in it's most efficient rpm range. You need to eliminate drivetrain slippage(if an auto get a lock up torque converter)and drivetrain drag(u-joint angles,heavy inefficient differentials,dragging brakes,etc.). Less weight means less work for the engine and less fuel burned.Each gallon of fuel has only a certain amount of energy and can only do a certain amount of work regardless of engine displacement.