evedder -
Welcome to EM! I used to want a Jeep Comanche back in the late 1980's, but I didn't have any money back then. There's plenty of big trucks getting great MPG here.
Think of it this way. When you have a lower starting MPG, a % improvement will be more measurable. This way, with good testing practices, you will be in a better position to "prove the mod" than others.
Also, you could set aside the money you save at the pump and put it into your "future MPG car" fund,
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CarloSW2