(FORTUNE Magazine) – JOHN D. BARR, 41 ASHLAND OIL Barr became CEO of Ashland's Valvoline Oil subsidiary in October and now heads the third-largest player (after Quaker State and Pennzoil) in the tough $2 billion U.S. motor oil market. His first concern: to shore up Valvoline's operating profit, down 42% at the end of the third quarter. His hopes lie in the opening of 100 new ''quick lube'' shops -- they change your car's oil fast -- in 1989, adding to 175 already operating. As president, he spearheaded Valvoline's huge, albeit late, entry into the trendy quick-lube business. ''We got into quick lubes when that idea was maturing,'' he admits. ''But now we dominate several key markets of the country.'' A native of Salmon Arm, British Columbia, Barr landed at Valvoline's headquarters in Lexington, Kentucky, after powering through the ranks of the company's Canadian subsidiary.

MOLLY K. BRENNAN, 28 GENERAL MOTORS For Michigan natives on the fast track since birth, there's an obvious place to go: GM, the world's largest company. Four years after Brennan finished setting 14 Michigan State University sprinting records and winning a Rhodes scholarship, she is a validation engineer at the company's Milford, Michigan, proving grounds. Her job is to test-drive models of future Chevrolet Corsicas and Berettas to see that they are up to government standards. Last November, GM picked her as one of six drivers of an even more exciting machine: the Sunraycer, a 360-pound solar vehicle that crossed Australia in six days to win the World Solar Challenge.

CHARLES L. DUNLAP, 45 PACIFIC RESOURCES As executive vice president, he oversees all of this Hawaii-based company's petroleum operations -- refining, marketing, and trading, which account for 90% of its revenues and profit. With negligible nearby oil deposits and a small local market for refined oil, the $950-million-a-year company is forced to look to the world beyond for business. No. 2 man Dunlap spends half his time traveling, buying cheap Asian and Alaskan North Slope oil and reselling it to East Asia and California. Pacific Resources' stock has doubled so far this year. Says Dunlap: ''The key thing we've done is develop a flexible strategy for crude oil acquisition'' -- avoiding long-term contracts -- ''so even with oil-price volatility these days we're well placed.''