But linear vs inverse depends entirely on what questions you are asking. If I want to know how much discretionary driving I can afford, MPG is a better measure

But linear vs inverse depends entirely on what questions you are asking. If I want to know how much discretionary driving I can afford, MPG is a better measure. If I want to know how much the car will cost to operate over fixed driving requirements (commuting, etc) GP100M is a better measurement. Maybe we can just have both ;-)