Most Americans (nearly 70 percent, in fact) have some weight they need to lose, but we rarely think that our cars could stand to lose a few pounds as well. When a car is redesigned or introduced, automakers often tout the fact that the new model is lighter than the old one, or is lighter than most competitors. It’s not like cars can suffer from diabetes or heart disease as a result of being overweight, so why do carmakers talk about car weight loss like they’re leading a Weight Watchers meeting?

The 2015 Ford F-150 lost weight
The Ford F-150 had a significant weight loss from 2014 to 2015. (Ford Motor Company)

To understand why automakers love to trim down their models you need to remember your high school physics. The energy or force required to move an object is equal to its mass multiplied by its acceleration. The less mass something has, the less energy is required to move it.

In automotive terms, the lighter the car, the less gas it needs to use to move and the better fuel economy it gets. That’s good for you, the car’s owner, and it’s also good for the automaker. In the U.S., car companies have to meet federally mandated Corporate Average Fuel Economy (CAFE) ratings. Those ratings stipulate that when the fuel economy ratings of all of a car company’s models are averaged, the average has to be below a certain mark. For the 2016 model year, carmakers that sell cars and light trucks must have an average fuel economy between 34.3 and 34.5 mpg for their entire model line. Squeezing out a few extra miles per gallon by losing some weight helps them achieve that goal.

Sometimes, car and truck models can lose a lot of weight in a redesign. The Ford F-150, for example, lost up to 700 pounds between the 2014 and 2015 model years. Other times, the weight loss isn’t as significant. The 2016 Chevrolet Cruze will weigh 250 pounds less than the 2015 model, which, given the current obesity epidemic, is like having one less passenger in the car. Can such a small loss really translate into fuel economy gains?

The answer is yes, it can (all the more reason to tell Kenny from IT you don’t want to carpool any more). For every 100 pounds a car loses, you can expect a 1 percent increase in miles per gallon. By dumping 250 pounds, fuel economy will improve by 2.5 percent, which will save you roughly seven cents on every gallon of gas. When it comes to the fuel economy standards that Chevrolet needs to meet for this year, having a 2.5 percent increase on the Cruze can help offset the impact of models, like Chevy’s large trucks and SUVs, as well as performance cars, that don’t have as good of fuel economy.

You don’t have to rush out and buy the newest, lightest car to save money on gas, however. Trim your car’s weight by removing things like bike racks, ski racks or rooftop carriers when you don’t need them. Clean out your car regularly so you’re not hauling around extra junk. And, yes, maybe talk to Kenny about finding another way to get to work.

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