[MetroMPG]

RH77 adds:

Exactly. So, put in a slushbox so people can drive it here. Classic PRNDL shift pattern. People use "D" and that's about it. BUT

Put a curious button somewhere that says "Economy". When pressed, the dash indicates "Economy" in green or something. Meanwhile, behind the scenes, the highest gear is now available and it shift's into a taller gearset at higher speed cruise. Normal operation ensues. Shut the car off, and like cruise control it resets. So you can go back to "D" and forget about stuff until you pass the gas station prices and "Hmmm, might as well press the "Economy" button today".