Good point, but GPHM has more syllables, and GPM makes it sound small;
but still, maybe 50, 25, 15, and 10 MPG could be expressed as 0.02, 0.04, <0.07, and 0.1 GPM.
Just drop the M - GPH/gallons per hundred is just as short and easy to say as MPG.
In Australia we say “litres per hundred”, there’s no point specifying kilometres because what else would it be?
OPM (Ounces per mile) seems to work out to nice numbers. A gas guzzler might use 13 OPM, where as a decently efficient sedan would be around 3. Plus we can keep our ridiculous American units, just the way we like them.
I was doing the metric equivalent.
The problem is mLs and ounces sound too small.
The good thing about 100 is that in turns mLs and ounces into liters and pounds, or gallons, as the case may be;
but that 100—I like units more than x-number-of-units as the basis of expression.
Nonetheless, I guess its GPHM, LPHKM, GPH, and LPH, until we come up with something better.
Then we have wp:natural gas vehicles and wp:miles per gallon gasoline equivalent, as LNG, CNG, and electric will probably become more common.
If 33.40 kilowatt-hours/mile ≈ 74.71 Mj/km
then if an electric car had an MPG equivalent of 40,
it’d be 0.835 kilowatt-hours/mile ≈ 1.87 Mj/km