The best replacement for gas mileage is speed.

The best alternatives to gas mileage are rated as following:
★★★★★  speed
★★★  diesel mileage
★★  tire size
★  tire pressure
★  octane
★  weight of car
  gear ratio
  electric mileage
  diesel
  gasoline engines mileage
  regular gas mileage

Your alternative for gas mileage is not listed? Suggest!
Speaking about gas mileage, one probably shouldn't forget about hybrid.

Other search terms related to gas mileage and their ratings are:
★★★★★ hybrid
★ cars
You have in mind a companion for gas mileage and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of gas mileage in all years. Click on graph for more.
gas mileage
speed
diesel mileage