Increasing numbers of car owners are going beyond that two- or three-times-a-year cleaning approach with their cars. They're picking up on a practice long-employed by new- and used-car dealers: detailing.

Automobile detailing basically is the deep-cleaning of a car. It includes such things as cleaning the engine and underside of the car; shampooing and vacuuming trunk interiors; carpet and upholstery cleaning; leather upholstery cleaning and restoration; removal of tar and cleaning of pinstriping and body molding; paint restoration, hand-washing and waxing.

It's called detailing because the people who do it don't miss even the smallest details. They have been known to use cotton swabs, toothpicks -- whatever it takes to get rid of unwanted and hidden dirt, grease and grime.

Professional Car Care Inc. in Rockville is one of the old-time local detailing firms, having been in operation for seven years. Owner Richard Plummer, 43, says his firm, which now deals only with private individuals, handles everything "from VWs to Rollses. We have between 600 and 700 cars that come in on a quarterly basis," in addition to one-time and new customers.

"People come in and want to know why my $69 wash and wax is better than their regular $6.50 machine-wash and hot-wax spray job," notes Plummer. They know the reason, he says, when they pick up their cars. Plummer's fee for a complete detailing job on a full-size sedan in average condition runs about $190.

Car Care Corp., an Arizona-based operation with around two dozen Detail Plus outlets around the country, plans to have more than 100 centers nationally -- including in the District -- and internationally by December 1985. The charge for a standard-size automobile is about $160.

Detailers can be found under Car Washing & Polishing in the Yellow Pages.