I have a hybrid car, which gives a constant read-out of your average fuel economy, as well as giving you little visual indicators while you’re driving of whether you’re driving it “right” (upshift/downshift indicators, and a big glowing ring around the tach which goes from green to blue if you rev higher or accelerate faster) and when you turn off the car, you get a bar graph showing how economically you drove it, as well as “achievements” and “levels” if you’ve been driving economically for a while.
But like all cars, your average fuel economy for the trip is going to be higher for a longer trip than a shorter one, because the first 5-10 minutes of the trip is warming up the engine and getting the cabin up to the right temperature, etc. So when I’m going for a short trip, like going out for lunch, and trying to choose between two destinations, I have this internal dialog where I first argue for the longer trip to keep the average fuel economy up, but then I have to forcibly remind myself that sure the average is higher, but so is the total fuel burn and it makes no sense to burn more gas just to get a better average.
Somebody told me a while ago that I have an “external locus of control”. I think I’m just a geek.