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San Luis Obispo Auto Repair

Engine Oil – A Necessary Evil

The oil that lives inside the engine of your car or truck is indeed a petroleum product and comes out of one of those sixty-six dollar barrels just like gasoline. It’s origin, use, and disposal has contributed to world wide environmental degradation just like it cousin, gasoline, and, like its’ cousin, it is a necessary part of daily driving. Inside your engine it lubricates in all temperatures, from Alaska to Death Valley, it prevents corrosion and oxidation, and carries away harmful by products of combustion including water, soot, particulates, and raw gas, all the while allowing itself to be ignored by everyone but the most conscientious driver.

Recommended replacement intervals for this hard-working substance are all over the map. Car manufacturers are typically recommending intervals of 7500 to 10,000 miles. Click and Clack of “Car Talk” fame recommend 5000 miles. We at Morin Brothers and most “quick lube” franchises recommend 3000 miles. So who is right? The best answer is “it depends”. The dependent variables are distance, time, and foot pressure on the go pedal. Trips of less than ten miles, stop and go driving, and rapid acceleration force the oil to store far more contaminants than steady state driving (Pizza delivery comes to mind, though having four kids in school may be a close second). Commutes of 20 miles or more and long trips are very easy on the oil. The engine is right up to temperature, the car rarely experiences cooling cycles, and heavy acceleration is unusual. So for one driver, the oil could be overdue at 3000 miles, and for another, a 3000-mile oil change would be too soon. Recommending a 3000-mile interval is a conservative approach. We’d rather be safe than sorry. The manufacturer’s recommendation is not based on ‘best practices”, but on a hypothetical “average driver” that drives 15,000 miles a year at speeds above 35 miles per hour and doesn’t want to spend more that $50 a year in maintenance. Not exactly your real life driver.

A more reasonable guideline might be time, not miles. If you are driving 16,000 miles a year and change your oil every three or four months you will be servicing your car between 4,000 and 5,000 miles - about right. If you are driving 6,000 miles a year and change your oil twice a year, at 3,000 miles between services, you are at a very reasonable interval.

The bottom line is that it is better to change your oil than not. In spite of the environmental impact, keeping your oil clean keeps your engine in good health, which extends the potential life of the car. The longer your can keep your car on the road, the longer you can postpone the much greater impact of disposing of it and manufacturing a replacement.


Driving green