It’s easier to convince an Evangelical that Christ was a grifter than to persuade pistonheads to give up their regular oil change. Yea, verily, the maniacal motorists believe in the healing power of regular visits to the Church of St. Pennzoil. And they certainly have the Gospel of Jiffy Lube on their sides: Thou shalt change thy oil every 3k miles or your engine will blow up in an explosion of fire and brimstone. Well I hereby give pistonheads permission to skip their next regularly scheduled motor oil change. And the one after that one. In fact, if you’re not planning to keep your car for all eternity, consider forgetting oil changes altogether.
Many decades ago, when metallurgy, tolerances, manufacturing precision and various aspects of engine controls (as well as the oil itself) were profoundly more primitive, the 3k mile oil change interval had a logical basis. Crude carburetor chokes caused overly rich mixtures, dumping raw gas onto cylinder walls that worked its way down into the crankcase. Poorly fitted rings caused blow-by, which had the same effect with nasty combustion byproducts. And poor tolerances created rapid wear, which released and circulated metal particles throughout the engine. People drove shorter distances, and cars often didn’t warm up enough to burn off contaminants. To travel 100k miles without an engine rebuild was a genuine accomplishment.
By the sixties, improvements in all of these mission critical areas led manufacturers to adopt an industry standard 6k mile oil change interval. Since then, recommended oil change intervals have risen as high as 10k miles. At the same time, many high end cars ECU’s (e.g. BMW, Porsche) now monitor engine and environmental operating conditions and calculate the ideal interval for an oil change– sometimes well into the teens.
When is the last time you heard of someone experiencing an engine failure (in normal use) that could be verifiably traced to damage from insufficient lubrication due to infrequent oil changes? Oil never wears out. It can become contaminated and certain additive characteristics can change. But in normal operational use in modern engines, this usually happens quite slowly.
And yet the 3k mile mantra can be heard everywhere: newspaper and magazine articles, on-line forums, radio talk shows and, of course, all the obvious and more subtle forms of advertising by the oil manufacturers and the oil change industry. When Jiffy Lube puts a sticker on my windshield warning me that my next oil change is due in 3k miles, it’s clear who benefits most from these regular visits, and it ain’t me or my car.
These days, it’s common to hear of documented engine life of 500k miles and more. A fleet of Chevy gasoline V8 pickups pulling trailers delivering car parts overnight all over the Midwest has run a number of bow tie bombers to over 600K without failure. A 1987 Saab 900 just hit the million mile mark without an engine rebuild. Yes, the Saab owner used expensive synthetic oil and changed it regularly in his million mile quest. But how long are you planning to keep your car?
Still not convinced? Da Vinci Code time. In the mid-80’s, Germany’s leading car magazine Auto, Motor und Sport ran a VW Golf with a 1.6 liter gasoline engine for 100,000 kilometers (62,000 miles) without changing the motor oil or filter. They then tore down the engine completely and examined every single moving part [microscopically] for signs of wear and tear. What little wear they could find was not engine life threatening and fit within normal operating parameters for the given mileage.
Obviously, I don’t expect pistonheads to forgo engine oil changes completely– if only because following manufacturer’s recommendations safeguards your potential warranty claims. Still, if warranty isn’t an issue and you’re not planning on keeping your car past 150k or so, and you run it under favorable conditions– a long commute, lots of highway miles, milder climate, etc. — consider extended intervals. If you have a three year lease, well, that’s between you and your conscience.
Meanwhile, the situation with gasoline and octane levels is roughly analogous. A couple of years ago, AM&S did another extensive test, running cars whose manufacturers called for premium fuel on regular gas. The result: performance and fuel economy losses ranged from zero to mid-single digit percentages. I don’t need to tell you that it can be a LOT cheaper to fill your car’s tank with a lower grade of fuel. And don’t worry about damaging your engine; modern detonation sensors constantly adjust ignition timing to be optimal for the fuel being burned and prevent pre-ignition.
Pistonheads who lavish low interval oil changes and high octane go-juice on the cherishd machines do so more for their own peace of mind than their car’s mechanical needs. It’s sweet, but unnecessary.