Eine Möglichkeit : price per liter (of) fuel

In GB gibt's Benzin inzwischen auch in Liter, aber in den USA sind es immer noch gallons, glaube ich, das müsstest du also eh umrechnen.

price per litre würde ich auch sagen, aber petrol/diesel statt fuel.

As Gibson says, 'gas' or 'gasoline' (and price per gallon) in AE, 'petrol' in BE (and litre with -re).

You can talk about fuel costs or fuel prices (probably typically in the plural) in a more general business sense, to predict expenses. The word 'fuel' includes other things like diesel, natural gas, and heating oil, which are also part of economic forecasts.

I wouldn't expect the word 'fuel' just for ordinary drivers talking about buying gas for their cars. Journalists reporting the price of gas week by week might sometimes use 'fuel' just for variety.

another possibility is:

A gallon/litre of gas is / costs....... Somewhat depends on what you are saying / stating and the circumstances.

Price per...of gas, somehow seems preferable in certain circumstances, though no one would question either expression.