@NathanG - There are some techniques that you can use to improve internal combustion engine efficiency. One of the easiest is to use the correct viscosity for your oil. Oil acts as a lubricant to enable your engine to move about freely as it does its work.
The correct viscosity will make your engine more efficient, improving your miles per gallon and generating less heat. I always pick the highest quality oil for my engine, even if I have to pay a little more, because it results in better performance and that puts money in my pocket in the long haul.