I gotta say, I'm with Bill (spectratone) all the way.. well.. with possible exception of the K&N filters, but that only from a cost standpoint...

Lowering compression (and spending a bunch of money to do it) is not the way to increase fuel economy. Get your engine in proper tune, and it will run as efficiently as it can.. again, depending on your driving style. Stick a thin board between the gas pedal and the floor (so you can't get full throttle) for a week.. see how much your mileage improves :-)

Keep in mind.. the difference between lowest available octane fuel and highest octane is what? 20-30 cents/gallon? Lets figure low and say you'll only spend $150 to lower your compression, and... probably not gain much (if any) in fuel economy... but to sacrafice performance... well, you do the math.

I'd say you're much better off spending that $150 on a thorough tunup, make sure everything is just right. Check tire pressure, take that pile of rocks out of the trunk (remember that snow storm last winter when you needed a little more traction?)

Do that, and you'll not only optimize fuel mileage, but you'll also optimize performance.
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-Matt I ♥ my ♂