Taking your time driving to your destination will cost you time, but save you money. GM says that by driving 65 mph instead of 70 mph, we could save an extra $5 dollars of gas for each extra hour we spend driving. For owners of large trucks and SUVs, the cost savings could be as much as $10 for each extra hour driven.
Side note - Accelerating evenly can help save gas too. Rapid acceleration can cost up to 12 miles per gallon.