An Iowa Department of Resources energy analyst offers some tips if you want to save some money in the wake of two-dollar-a-gallon gas. Jennifer Moehlmann says some minor adjustments in driving habits can pay off. Your speed, for example — she says every five miles an hour you drive over 60 mph adds 10 cents to the price of every gallon of gas you burn. Moehlmann says a little planning helps too. Combine your trips, don’t let your car idle if you can avoid it, and look into ethanol and biodiesel as they’re usually cheaper. While she says it’s best to avoid letting your car idle, she says there are situations where that doesn’t apply. She says at a short red light you don’t want to turn your car off, but if you’re stopped for a long train, you should turn off the engine. Moehlmann say you should be sure your car is tuned up and the tires are properly inflated.