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.
Yeah, I was thinking about the same sorts of things. I think ounces are okay but not great. I cook a lot and have a good intuitive grasp on fl oz, but I’m not sure everyone does here. I wish we had a good unit bigger than miles/kilometers to use with liters/gallons. Leagues are still too small and megameters are too big, but both of those have the advantage of sounding awesome… and disadvantage of not being commonly used.