"每英里汽油消耗量" can be translated into English as "gasoline consumption per mile" or "fuel consumption per mile" (if referring to fuel in a more general sense, though gasoline is the most common context for cars in the US).
In some technical or formal contexts, you might also see it expressed as "miles per gallon (MPG)"'s inverse concept (though MPG itself is a direct measure of efficiency), but for a direct translation of the phrase "每英里汽油消耗量," the first two options are most accurate.
For example:
"The gasoline consumption per mile of this car is quite high."
"We need to improve the fuel consumption per mile to save costs."