fuel consumption rate vs mileage

fuel consumption rate and mileage both are nouns.

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

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

fuel consumption rate and 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, gasoline mileage.

fuel consumption rate (noun)	mileage (noun)
the ratio of the number of miles traveled to the number of gallons of gasoline burned	distance measured in miles
	a travel allowance at a given rate per mile traveled
	the ratio of the number of miles traveled to the number of gallons of gasoline burned