That old joke about a race driver luring an unsuspecting buyer by assuring, "My car's only been driven on weekends," doesn't apply to many racers today. Drivers of showroom stock cars in Sports Car Club of America meets are finding that the easiest way to get their cars from track to track is to drive them.

"I've put 16,000 miles on my new Saab this season, and very little of it on the track," said Don Knowles of Springfield, who leads the showroom stock sedan class. Southeastern Division. "I sometimes fly to races, but my crew drives the car. We put a rack on the top, load up the tires and tools and go."

Knowles has won races in Florida, Georgia, Texas and Colorado this year. "I would like to race closer to home, but I have factory support from Saab and they already had a driver in this area." he said.

Knowles will race just twice more this season before the national championship run-offs, for which he has qualified. "I had six races in eight weekends in June and July and I'm a little bushed now," he admitted. "There's a chance I could lose the divisional title by a few points, but I'm in the run-offs, which is important."

All this seems a bit improable for a Department of Agriculture budget analyst, which is what Knowles is. He's been a racer for six years and does much of his own mechanical work.

"You can't fiddle too much with a showroom stock car, so any dealer can check it over too. Walt Koopman in Bethesda has been a big help to me, when I'm in this area."

There are several other local racers who travel far afield to seek fame and fortune. Bob Tullius is now a oneman team for Group 44 of Herndon. Driving a Jaguar XJS, he now stands second in category I Trans-Am Championship points to John Bauer, a Porsche driver.

Today's race at Mosport, Canada, could put Tullius in first place, if he wins his class.He has foregone amateur races to concentrate on this proseries for sports sedans.

Until this year, Group 44 fielded three or four British Leyland cars in SCCA amateur events. The team was reduced to one car, the Jaguar, and one full-time driver. Tullius this season, Engine expert Brian Fuerstenau, several times a national champion, makes a race now and then to keep his hand in.

Nick Craw of Millwood, Va. is now a strong second in the International Motor Sport Association's Executive Home Challenge for small sedans. Driving a BMW, Craw won the season's opening race, has added four seconds and two thirds since and now trails Don Devendorf, who steers a Datsun.

Craw, and defending challenge champion Carson Baird of Laurel have won more races in this six-year series than any other driver, with 11 wins for Craw and 10 for Baird. Baird has had a bad year in his Plymouth Arrow, with his only points coming from a second place in a race last month at Hallett, Okla.

Drag racing stars can compete on several circuits far from local strips. R.C. Sherman of Rockville is among the top 10 in Pro Funny Car points in the Winston Cup CHallenges sponsored by both the International and the National Hot Rod associations.

Leon Miranian of Washington, driving a stock class sedan, is second, in the International group's standings. Bob Pecker, Silver Spring, runs a Super Stock on the National circuit and his earned points in his class.