Miles per gallon (mpg) is not the only way to measure fuel economy. Several recent articles suggest that gallons per mile (gpm) may be a better measure of gas mileage. In fact, gpm is the standard used in Europe to measure fuel costs (who measure fuel costs in liters/100 km).
Researchers from Duke University’s Fuqua School of Business report in the June 20, 2008 issue of Science magazine, that posting a vehicle’s fuel efficiency in gallons per mile rather than miles per gallon would help consumers make better decisions about car purchases and environmental impact. Here’s how: Take three different cars with three different mpg ratings, and drive them each 100 miles. Each vehicle will burn a different amount of gas to drive that 100 miles. For example:
12.5 mpg = 8 gallons per 100 miles
25 mpg = 4 gallons per 100 miles
50 mpg = 2 gallons per 100 miles
The numbers are there, but what, really, do they tell us? The results actually reveal two things:
- Trading in a gas hog for a mid-size sedan provides considerable fuel savings.
- Trading in a mid-size sedan for a high-mileage hybrid doesn’t really save you that much in fuel costs.
The numbers also indicate that although fuel economy gains from 12-20 mpg are notable, once vehicles get over 25 mpg, the gains aren’t as substantial. And the results also tell us that while they are a great deal more eco-friendly, hybrids don’t save much more gas than mid-size sedans.
Thinking in terms of gpm can help consumers make more informed car-buying decisions. For example, if you’re trying to decide between an SUV that gets 15 mpg and one that gets 18 mpg, you may think that there’s really not much difference in gas mileage. It’s only a 3 mph difference, right? But if you look at the gpm, the 15 mpg SUV uses 6.6 gallons to travel 100 miles, while the 18 mpg SUV uses only 5.5 gallons. In about a month of driving (or 1000 miles), the 18 mpg SUV would use 11 gallons of gasoline less. Think of how much you could save in a year!
So how do you determine a vehicle’s gpm? That’s easy! Simply divide 100 by the vehicle’s miles per gallon. For example, if your vehicle gets 27 mpg, you would divide 100 by 27, which would give you a gpm of 3.7.
Remember, when shopping for a new vehicle, it may be a wise idea to compare both the mpg AND the gpm of the vehicles you’re interested in to get a better idea of the true fuel economy.
