Michelle Jordan of Silver Spring asked me if I knew why the Mr. Wash Car Wash in Kensington changed from a full-serve lathering to an "Express Wash."

I didn't, but I told her I thought it was a good question. And that unleashed the floodgates: What's the difference between a "cheapo wash and an expensive wash?" she asked. And how come I don't get coupons for Mr. Wash in my Comcast bill anymore? And if you get an expensive wash with various add-ons, like rust inhibitor or wax, how do you know you're actually getting those extras you've paid for?

I was struck by several elements of the conversation. First, Jordan's inquiries, expressed with a genuine mix of concern, alarm and irritation, show what happens to customers when favored retailers change something but don't explain why. I was also reminded how many services we use regularly that we don't really understand. And third, I was reminded that I've always wondered why there seem to be so few self-serve carwash bays in the Washington area.

What better time than after a winter like we've had to try to learn a little bit more about the carwash business?

As it turns out, the decision by Mr. Wash to switch its once full-serve carwash to an express service at this location is part of an industry trend. Carwash operators are looking for ways to reduce their need for costly employees, while at the same time trying to offer a service that will appeal to as many customers as possible.

There are now about 7,500 of these "express" washes -- some operators called them flex washes -- nationwide, up from 5,000 two years ago, according to the International Carwash Association in Chicago. And the number of full-service washes has declined from 10,000 two years ago to 7,500.

Express washes use the same "tunnel" setup as a full-service carwash, but at an express wash there is no team of workers vacuuming the inside rugs and cleaning the interior windows, as is the case in a full-service wash. The driver also stays in the car throughout an express wash as the outside of the car is cleaned by the same machines inside the tunnel that a full-service wash uses. There may or may not be a wipe-down at the end. The cost for express wash can be half what a full-serve wash costs.

At other Mr. Wash locations, a full-serve runs $12 to $18, and an express wash would be $6 to $10, said Steve Harris, owner of the local chain. Harris said he's converting some of his full-serve washes to the express format and opening new washes with an express setup. "Customers like it," he said.

Why the nationwide rush to the "cheapo" format, as Jordan calls it?

"The problem is getting and keeping decent labor," said Mark Thorsby, executive director of the carwash association. "The other piece is the consumer. . . . Not all customers want the inside of their vehicle cleaned at all times."

Mr. Wash employs 200 to 300 people, depending on the season, at his eight local carwashes, but his labor needs are gradually dropping as three of his outlets are now express wash centers. Not only does Harris need fewer workers on hand for an express wash, but he doesn't get stuck paying those same employees if he has to close because of rain or snow.

During this unusually rainy and snowy winter, Mr. Wash has had to close repeatedly. Harris said he tries to give his full-service employees some work cleaning equipment, but no one makes as much money as he would if the carwash were open -- not Harris, and not the workers.

"Some places, like in California, where it never rains, it's a little easier to operate and it might be more profitable," Harris said.

The weather is a major factor in the carwash business. The two busiest seasons are winter, when people want to have road salt washed off their cars, and spring, when pollen settles in. But too much bad weather is bad for business, Harris said, because no one wants to get a car washed right before a rain or snow storm. The best weather pattern is to have a storm, then a week or two of sunshine.

But express washes may help ameliorate some of the weather-related peaks and valleys, industry experts say. A driver with a dirty car might not be willing to pay $15 for a full-service wash if rain is forecast for the next day but might be willing to fork over $6 or $8 for an express wash. Plus, on the days an express wash is open, it can squeeze more cars through. That's a bonus for express-wash owners, since it costs $2 million to build a tunnel-based carwash, according to Thorsby of the ICA. The last benefit to express washes, as the industry sees it, is that some customers, such as mothers with children in the back seat, don't want to get out of their cars. "Sixty percent of conventional carwash customers are women," Thorsby said.

That may not satisfy Jordan, but it seems to be a pretty unstoppable movement in the industry. And I must say, I rather wish there were an express wash near me, because I think I might use it more. As it is now, I use a full-service wash on Connecticut Avenue about once every three or four weeks and frequently feel my car is dirty in between.

Another answer for my in-between washings might be a truly self-serve carwash, with a wand you hold yourself and pay for with quarters. But there aren't any of those in the city, or even in the close-in suburbs. Chalk that up to high land costs, unfavorable zoning, onerous permitting and unwelcoming neighbors, said Dave DuGoff, incoming president of the Mid-Atlantic Carwash Association and owner of the self-serve College Park CarWash.

"A full-service can squeeze onto 15,000 to 20,000 square feet," DuGoff said. "I'm sitting on an acre and a half of land, about 70,000 square feet."

Incidentally, DuGoff's eight self-serve washing bays include two that are called touch-free automatics, in which automated washers circle your car for a price comparable to that of an express wash.

Having seen how many types of carwashes are out there now, I'm feeling rather cheated that my choices in the city amount to paying $15 for a full-serve wash or washing my car myself at home, a choice that has all kinds of water-use and environmental drawbacks. I might as well pour a bottle of Palmolive into Rock Creek.

Of course, the carwash industry can't satisfy everybody any more than any other retailer can. But at least the industry seems to be trying. Having four types of carwashes is a lot better than having one.

But as the industry evolves and carwash owners like Harris switch formats, it'll be important to remember Michelle Jordan or any other regular customer. She may not like the express wash, but if the change were communicated and marketed properly, she might not feel so betrayed, leading her to question the company's motives. A good lesson to any retailer.

So, in closing, here are the answers to Jordan's other questions:

Mr. Wash stopped sending coupons with Comcast bills because Comcast won't allow it anymore. But the company still puts coupons in the newspaper, online and in direct mailings.

And to tell if you're actually getting the add-ons you might buy in a full-serve wash, Harris of Mr. Wash says, a driver can look at the lights that go on inside the tunnel during the wash to indicate which features are being activated.

Thorsby of ICA has a better idea for people who have such doubts. "I tell people to find the owner, and make him prove it."

If you have a question, comment or concern about what you see when you shop, write to Margaret Pressler at sellingus@washpost.com.