I thought I'd share some info with everyone about how to increase your gas mileage while driving on the highway. The methods I am going to share were learned during numerous trips from Chicago to Champaign and vice-versa. These methods work very well for me and my car (94 Saturn SL1).
Oh and a couple of side notes, if the temperature is below 50 degrees, don't bother trying these techniques. The cold weather really kills gas mileage. Also, strong head and crosswinds seem to always mess up my gas mileage. Forget trying to save gas with strong winds that aren't of the tail persuation.
Ok, the most important thing about trying to get good gas mileage is to keep the speed relatively low. You want a speed which requires very little gas pedal pressure. For my car, this is about 65mph. Finding your ideal speed isn't too hard. Wait till your car shifts into it's highest gear and then push down slightly on the gas pedal. Wherever your speed ends up (while on a flat strech of road) that is your ideal crusing speed. Take note of the RPMs of your engine at this speed. It is of the utmost importance that you keep your pedal pressure and RPMs the same. No hammering the pedal to pass people. No speeding up and slowing down. You want to maintain CONSTANT speed and RPM level while on a flat road damnit! While going up hills, do not let your car downshift. While going down hills, lay off the accelerator a little. Obviously these techniques will not work with cruise control, so turn the bugger off. Ok so lets recap, 1) find your ideal low pedal pressure crusing speed 2) on the flats, maintain that speed as closely as possible 3) on the hills, make sure to keep your RPMs level, you will lose speed up the hill 4) while going downhill, lay off the accelerator a little
To give everyone an idea of just how much your gas mileage can improve, here's some numbers. If I drive at 70-75 and don't worry about downshifting or keeping my speed constant I get about 32mpg. If I'm really concentrating on getting good gas mileage and adhering to my aforementioned techniques, I can get up to 45mpg. That's a pretty big difference.