I Need A Vacation
Lowering a car is not going to increase your MPG. Car manufacturers spend millions on testing and wind tunnels to get the most efficient design by changing the design ie. lowering your car you might actually decrease the MPG because you've changed the a tubal design flow of the vehicle.
I was thinking exactly this. I did a little cost comparison when I was buying my Civic. It was between this 40 mpg Civic and a different 35 mpg car. Over 170,000 miles the gas savings would be about $1500. That's $300 per mpg, over the course of 9 or 10 years would be like a $30 savings per year per mpg.
Maybe lowering the car would give you a 2 mpg increase, and if it cost you $2000 you'd have to drive that car 425,000 miles just to break even (read: break even, meaning you havent saved a single penny yet). That's not even including the extra cost of low profile tires (if you count that, you'll probably never break even).