Fuel Economy And Fuel Efficiency Are Not The Same - Here's The Difference

Fuel economy and fuel efficiency get used interchangeably all the time, but they're not actually the same thing. One is a specific measurement, and the other's more of a broader concept. Knowing which is which can make all the difference, both for a vehicle's performance and estimating its fuel costs. It's all about looking beyond the traditional mpg figure to see the big picture.

In the simplest of terms, fuel economy is miles per gallon (MPG). It gives you an estimate of how far a vehicle can travel using one gallon of fuel. On paper, a sedan rated at 30 mpg can travel 30 miles on a gallon of gasoline. But fuel efficiency will tell you how effectively that sedan actually converts that fuel into motion. If it's too big, too heavy, or driving too fast, fuel economy can take a hit. For that reason, a vehicle can have an efficient engine, but poor fuel economy.

This nuance between fuel economy and fuel efficiency is why some are pushing to measure fuel consumption by gallons used over a fixed distance rather than miles traveled per gallon. The argument is that gallons per 100 miles gives drivers a more accurate description of how much fuel a vehicle burns, not unlike the calculation to find MPGe.

Automotive researcher Edmunds says it best. In its example, an SUV with a fuel economy of 12.5 mpg uses eight gallons to travel 100 miles, but a sedan with a fuel economy of 25 mpg uses four gallons over the same distance. Likewise, a 50-mpg hybrid would need two gallons. By thinking of it this way, Edmunds explains, you can see both fuel economy and fuel efficiency in one metric... revealing "how much gas is saved in each case." 

Sticking with Edmunds' exercise, think about a 25-mpg sedan and a 50-mpg hybrid. Fuel economy would make you think the hybrid is more efficient than the sedan because the mpg figure doubles. But in reality, the difference is only two gallons saved per 100 miles. Meanwhile, a 25-mpg sedan saves four gallons over a 12.5-mpg SUV using eight. That's better fuel efficiency.

Here's what to take away from all this math: Fuel economy measures distance traveled per gallon, while fuel efficiency tells you how effectively a vehicle uses fuel overall. To get the best picture, think in terms of fuel consumption rather than fuel economy alone.