DETROIT-Today's motor oils are designed to satisfy the demands of modern car and truck engines, which run at higher speeds and temperatures than engines of the past. That means the automakers' recommended oil change intervals have gotten longer. With some cars, manufacturers say that under normal driving conditions you can wait 9,000 or 10,000 miles between changes, or sometimes up to a year.
But the quick oil-change industry and many mechanics still recommend new oil and a new filter every 3,000 miles to protect the expensive machinery. They say that is especially important if you operate your car under severe conditions-drive on dusty or salty roads, make many short trips or haul a trailer.
Experience shows that most car owners think their daily driving conditions are normal. So how do you play it safe?
Is a 3,000-mile interval too short? Does it waste money, produce excess waste oil that must be disposed of without fouling the environment and also deplete a finite natural resource?
Shell International and the German automaker Mercedes-Benz are looking into the possibility of a sensor that could help resolve the debate. It would measure the condition of engine oil and signal a driver when it was time for a change.
Engineers for the companies discussed their research at this year's congress of the Society of Automotive Engineers. They have concluded that the maximum time limit for oil changes should be 12 months but say time periods or mileage intervals are not the best solution.