Q: My filth-encrusted Mini Cooper and I have just moved from the valley of plentiful car washes, San Fernando, to Portland. I’ve spotted a few car washes here and there in my new neighborhood, but it’s nothing like Southern Cali where it’s car washes for as far as the eye can see. Here’s the thing: I have a nice long driveway, plenty of garden hose, a pile of old beach towels, and I need to work on my tan … you know what I’m getting at. I also wouldn’t mind saving a few bucks by giving Mini a bath myself. But I’ve heard that performing a DIY driveway scrub-down is an eco no-no. Should I seek out a commercial car wash like I’ve done in the past?

Dirtily yours,

Rose, Portland, Ore.

A: Hold off on donning that bikini and stick with what you know. Sorry to hear that finding a decent car wash joint in your new Portland ’nabe isn’t as easy as it was in SoCal, but make it happen (but please, don’t drive all over tarnation on a mission to rinse off your ride). Washing Mini in the comfort of your own driveway could be a fun weekend afternoon-in-the-summertime diversion, no doubt, but the toll that it’ll take on the environment is pretty harsh compared to a spin through a commercial wash.

Here’s why: commercial car washes, both in-bay automated ones that you’ll find at gas stations and self-serve establishments where you can DIY, use much less water and they’re required by law to drain that nasty, murky wastewater into municipal sewer systems where it’s treated.

Let’s look at some figures for comparison: the average at-home car wash uses 80 to 140 gallons of water while a commercial one uses about 45 gallons of H2O. How’s this possible? The heavily regulated commercial car wash industry is actually keen on water-saving techniques and most legit businesses employ all sorts of fancy, advanced nozzles and pumps. It may seem like a ton of water is used at those super-fun in-bay automated car washes, but in reality it’s much less than what you’d use from a garden hose.

Just as taxing on Mamma Nature as excessive water use is the pollution associated with at-home car washing. When doing the dirty deed, untreated water rushes straight into storm drains, taking with it motor oil, dirt, exhaust and rust, not to mention whatever soaps and degreasers you are cleaning with.

From there, the chem-ridden H20 is dumped into local waterways – in your case, the beautiful Willamette or Columbia rivers – where it’s a threat to aquatic wildlife. It’s straight-out nasty. Just imagine dumping a small bucket of motor oil, a fistful of dirt and a sprinkle of rust directly into the Willamette … these aren’t exact amounts, of course, but that’s pretty much what happens when you wash your car at home.

Before you settle on a commercial car wash, do a bit of asking around to see how seriously a business takes the art of eco car washing. It’s a given, thanks to the Clean Water Act, that the nasties scrubbed off of your Mini will be treated, but some businesses go a step further. I recommend Portland’s ECO Car Wash chain.

I don’t drive these days so I’m not fully invested in the world of automobiles, but every time I see someone washing a car on the street, I cringe a little. Don’t be one of those people who make this non-drying, water-sensitive green advice columnist cringe. Treat Mini to a commercial car wash. And wear your bikini if you must.

Got a question? Submit a question to Mother Nature and one of our many experts will track down the answer. Plus: Visit our advice archives to see if your question has already been tackled.

Photo: Ted S. Warren/Associated Press

MNN homepage photo: lenm/iStockphoto 

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.

Is washing the car myself an eco no-no?
A DIY car wash can be fun, but the toll it’ll take on the environment is pretty harsh compared to a spin through a commercial wash.