Better engines have made obsolete the rule about changing motor oil every 3,000 miles or three months.
So what are motor oil marketers to do, especially since three of the largest companies are tied to quick-change oil outlets?
The companies are chasing owners of older vehicles. They also are dividing the market into segments and targeting advertising at those segments.
In Europe, auto makers' guidelines call for oil changes every 5,000 to 10,000 miles.
Industry executives predict such extended intervals could become commonplace in the U.S. in a few years. That's when auto makers are expected to release their next round of specifications for motor oil.
``We are keeping an eye on it because we don't want any surprises,'' said Tami Talbert, global strategy manager of Royal Dutch-Shell Group's Pennzoil and Quaker State brands.
Owners' manuals for new vehicles call for oil changes an average of every 5,000 miles, Ms. Talbert said.
Rolf Linder, vice president of marketing at Ashland Inc.'s Valvoline subsidiary, said the company tends to recommend oil changes at 3,000 miles or every three months.
But with certain engines and premium motor oils, ``you could run the product for a year without changing the oil,'' Mr. Linder said. ``But we don't recommend it.''
Motor oil marketers are placing greater emphasis on high-mileage vehicles.
Nearly two-thirds of all automobiles in the U.S. have 75,000 miles or more on their odometers, according to the industry researcher NPD Group of Port Washington, N.Y.
Sales of high-mileage motor oil by seven major auto parts chains rose to 7.7 percent of all quarts of oil sold in the 12 months that ended in July compared with 3.3 percent for the year-ago period.
High-mileage oil ``is one of the primary growth areas of our business,'' Mr. Linder said.
Valvoline's MaxLife-specifically manufactured for high-mileage engines-leads high-mileage motor oil sales by auto parts retailers, according to NPD reports.
Valvoline is targeting customers according to the type of vehicles they drive. The company touts its DuraBlend Tough Driving synthetic formula for truck and sport-utility vehicle engines.
Quaker State's market share has slipped in the past few years.
Ms. Talbert said that Shell seeks to distinguish the Pennzoil and Quaker State brands according to the benefits they offer different groups of consumers.