[SECProto]

Fuel is sold by volume, which is why volumetric fuel efficiency is desirable to the consumer

[saalweachter]

Fuel is sold by volume and fuel type; diesel is about 25% more expensive per gallon than regular gasoline where I am.

[SECProto]

Correct - where I am it is cheaper most of the year, a bit more expensive in the winter.

[andruby]

And it is 10% cheaper than gasoline where I am (South-Africa)