On the car side of things, people seem to appreciate efficiency in cycles. Back in the OPEC crisis period 70s, quite a few cars had optional gages that indicated whether you were wasting gas or not (based on a simple vacuum measurement). After market providers also allowed users to add these gages to the cars they already had. By 76 Cadillac had meters in their cars giving instant MPG, and average MPG in real-time digital readouts. I recall contemporary articles either fell into two categories … people who responded by trying to get the best possible number and those who found it depressing.

A final note on meters of this type goes to accuracy … almost any new car with enough of an enthusiast following to have a website will have at least one discussion forum devoted to gas mileage; the majority of these discussions come to the conclusion that the dashboard readouts for fuel consumption are universally optimistic. The fill-drive-fill method is still the most accurate, but the distance between feedback loop between this and driving technique is obviously too open. To me this suggests that the greatest value in instant MPG measurement would be in identifying relative changes… a task that might not be best suited by inaccurate, rapidly changing digital displays. The old vacuum units had analog needles or stoplight-like red/yellow/green 3 light displays.