Typical bike engine is about .45 pound per HP per hour in fuel.
Best giant diesel container ship engine is about 35-40% of that rate of consumption.
Best passenger car engine listed on Wicki is the 5 cylinder 1990 Audi direct injected diesel at about 45-50% of the typical bike engine. Best gas engine in a car is the Prius motor. Possibly the lean burn engine in the first gen Insight might be better than the Prius when in lean burn.
There may be others that are slightly better but I got tired of looking
.
I'm sure Frank can find a few.
regards
Mech