Want to save gas? Clean out your car.

Lugging around even ten pounds of extra weight in your car can have a significant financial impact. Lightening the load will increase fuel efficiency and prolong the life of your car.

Depending on the specific model, your car loses 1-2% fuel efficiency for every 100 pounds of extra weight in the car. That’s a surprising amount that can really add up.

For example, let’s say you’re matching the extra weight that a friend of mine (who we’ll call Cathy) carries in her car. She consistently carries (mostly) unused car seats in the back seat of your car, plus she hauls around a box of books in the trunk along with a few other excess items. The sum total of that extra load is about 70 pounds.

That means, depending on the model, Cathy is burning an extra 0.7 to 1.4% in gas just due to this extra weight. Let’s say it’s 1%.

If her car gets 20 miles to the gallon with the weight in it and she commutes, putting 20,000 miles on it per year, she’s burning 9.9 extra gallons of gas per year just due to carrying the extra junk.

Say goodbye to $33 or so a year in just fuel costs, Cathy, never mind the additional wear on all of your car’s components.

Even a slight difference of just ten pounds can have a real financial impact. Let’s say you’re driving the same car Cathy is, where you’re getting 20 miles to the gallon and you’re driving 20,000 miles per year. That 0.15% in additional weight is eating up 1.5 gallons in gas per year, costing you about $5 in additional fuel along with slight additional wear on your car.

The message here is clear: get the excess weight out of your car.

How can you do that? Simply make sure that you’re not carrying anything unnecessary in your trunk or your backseat. Evaluate what’s in there and get rid of the things that you don’t need to be carrying back and forth.

I’m constantly amazed at the things people carry in their trunk, from huge assortments of shoes to large gun cases. These things add weight to the car and you pay for that weight directly at the fuel pump and indirectly whenever you get maintenance work done on your car or need a repair done.

There’s only one exception to this rule that I’ve found. If you’re seeing any chance of icy roads, it’s worthwhile to have extra weight in your car because it improves your traction and keeps you safe. I often carry that extra weight in the form of sand bags or rock salt, both of which can help you in a rough winter situation. The extra safety is well worth losing a few percent in fuel efficiency for a season.

Aside from that, you’re only saving money and helping your automobile’s lifespan by reducing the load you’re carrying. If you’re not hauling it around for a purpose, don’t haul it around.

This post is part of a yearlong series called “365 Ways to Live Cheap (Revisited),” in which I’m revisiting the entries from my book “365 Ways to Live Cheap,” which is available at Amazon and at bookstores everywhere.