One way is definitely more eco-friendly.

Sponge with soap and water
Credit: Aya Brackett

Want to save money? Then you know the deal: Haul out that hose and sponge. Want to save time? Also a no-brainer: Drop by the car wash on your way home. But if you’re looking for the more earth-friendly way to clean your wheels, the answer may surprise you.

When you scrub your sedan at home, the dirty water, tinged with traces of motor oil, antifreeze, and gasoline that your car has picked up on the road, runs down the driveway and into storm drains, which empty into local rivers and creeks. This runoff can coat the gills of fish (and tadpoles!) in these smaller waterways, suffocating them. Detergents also cause harm.

On the other hand, the runoff produced by an automatic car wash (or even a guy who washes your car at a gas station) is subject to wastewater laws. That means either it goes to the local sewage-treatment plant, where it is filtered and cleaned, just like the water from your pipes at home, or it is recycled on-site by the business. The leftover gunk is disposed of at a landfill. Automatic car washes also tend to use as little as 30 gallons of water per car; at home, with a regular garden hose, you’ll use that amount of water in about four minutes. So give yourself a guilt-free break and let the pros handle the job.