fuel consumption rate vs gasoline mileage

fuel consumption rate and gasoline mileage both are nouns.

Word	Noun	Adjective	Verb	Adverb
fuel consumption rate	Yes	No	No	No
gasoline mileage	Yes	No	No	No

As nouns, fuel consumption rate and gasoline mileage are synonyms defined as:

fuel consumption rate and gasoline mileage: the ratio of the number of miles traveled to the number of gallons of gasoline burned

Other synonyms of fuel consumption rate include gas mileage, mileage.

fuel consumption rate (noun)	gasoline mileage (noun)
the ratio of the number of miles traveled to the number of gallons of gasoline burned	the ratio of the number of miles traveled to the number of gallons of gasoline burned