I don't know why this concept is so hard to grasp for some people. If the engine is most efficient at a certain RPM, that is exactly the RPM that will get the greatest fuel economy. I'm not talking about max horsepower or max torque, I'm talking about the RPM at which the greatest -percentage- of heat energy is converted to KINETIC ENERGY. This is going to be the most fuel-efficient RPM for the engine, because the engine is producing the greatest ratio of output kinetic energy in relation to rate of fuel consumption. Now, what some people are failing to grasp is that the engines that these facts apply to are (duh) used to provide kinetic energy to accelerate an automobile and keep it moving. Nothing could be simpler, IMHO. Yet it seems to go right over the heads of many people.
Simple question: If you know the RPM that your engine is most fuel-efficient at, are you only going to run your engine at that speed while the car is in Neutral? Because that is the only way you can avoid maximizing the fuel efficiency of your automobile if you are running it's engine at the most fuel-efficient RPM. -Dave
