When anticipating a stop of more than seven seconds, Gerdes says it's best to turn off the engine. Whether it's a long red light, the line at a fast food restaurant or waiting outside for children at the mall, Gerdes says killing the engine and rolling down the window can save gas. When a vehicle's engine is running and it isn't moving, the vehicle is getting zero miles per gallon.

"You wouldn't necessarily turn your car off at every single light, but if it's a three-minute light and it just turned red, shut that thing down. Hybrids do that automatically and you should, too," says Gerdes.

Few drivers will ever be able to attain the efficiency some notable hypermilers get, but Gerdes says using a few of the tips can lead to a big savings. Increasing fuel efficiency by 20 percent would be the same as knocking bringing down that $4 gallon of gas to $3.20, and those who can double their fuel efficiency are cutting fuel costs in half. Gerdes says without making a single modification, the entire country could increase its fuel efficiency by 20 percent by simply driving better.

"I am paying (the equivalent of) less than $2 per gallon by the way I drive. If someone were to put up a sign with gas for $2, people would be lined up for a hundred miles. We have control of that through the way we drive," says Gerdes.

15 more ways to slash fuel costs

1. Slow down: The U.S. Department of Energy says most vehicles get their best fuel economy at speeds between 40 and 55 miles per hour. Efficiency decreases rapidly at speeds over 60 miles per hour.

2. Blow up: Inflate your tires to the maximum pressure indicated on the tire's sidewall.

3. Link your trips: Start with the destination that's farthest away. Doing this assures that your car will be warmed up fully on the way to the first destination before you begin making a number of starts and stops.

4. No idling: Don't let your car idle for long periods of time. Most engines only require seven seconds of gas to restart, so it's more efficient to turn the vehicle off at long red lights, drive-throughs or other places where you might be waiting.

5. Tune up: Keep your car properly maintained by changing the oil and air filter, balancing your tires and aligning your wheels as directed by your owner's manual.