Many drivers assume that if they want to reduce their fuel costs, they'll have to trade in their current car for a compact that gets 40-plus miles per gallon. While this can obviously help, a recent study showed that a driver's own behavior and choices can reduce the money they spend on gas by as much as 45 percent.

Two University of Michigan researchers looked into the many factors that affect fuel economy and determined that a majority were under a driver's control, rather than simply tied to the car they drive. For example, a vehicle that is not properly maintained uses a lot more fuel. The study showed that regular oil changes, tune-ups and properly inflated tires can go a long way toward keeping fuel costs low, reports USA Today. The duo characterized these as "strategic" decisions.

"Tactical" choices were defined as those related to a specific trip. This is mostly tied into choosing out a good route. The study recommends avoiding hills and any highways that are known to have traffic, as starting and stopping really kills MPGs.

Once on the road, the way you drive also comes into play. Going slow and conservatively using the brakes can save quite a bit of fuel, as can turning the air conditioning off.