lowering revs is the best way to get better milage. Very close to that is making your car lighter. To get best economy you want a cam that optimizes low rpm power, good flowing exhaust, and a well tuned fuel injection system. But you can still get good mileage withough the wussy cam and FI. I get 20 mpg in my 67 mustang with a 300 rwhp 302, 3.80 rear gears and a 650 DP holley tuned for max power. The only thing I have that says "milage" is my t5 transmision with a .68 overdrive.