Save at the pump
A large portion of what people spend on rental cars goes to fuel. But you can cut back on fuel spending. First, choose a fuel-efficient rental car. Many of the national car rental companies have online lists of fuel-efficient vehicles available, such as the Hyundai Accent, Ford Focus, Toyota Prius or Nissan Altima.
Second, use a GPS to make sure you're not unnecessarily driving extra distance, but rather than paying extra for a car equipped with GPS, buy your own, says Carol Margolis, author of "Business Travel Success: How to Reduce Stress, Be More Productive & Travel with Confidence."
If you use a smartphone equipped with GPS, you also can utilize the mobile app GasBuddy, which shows you the cheapest gasoline nearby.
Finally, don't pre-purchase gas from the car rental company if you expect to have time to fill up the tank before returning the car. If you buy gas from the rental company, be sure to drain the tank. On a recent trip, business owner Bowen Gines purchased a tank of gas at $3.99 per gallon from the rental company only because local gas stations were selling gas for $4.25 per gallon.
"It sounds like a good deal, unless you bring the car back with a half tank of gas, which we did," Gines says. "Then they make an additional chunk of change for each car."