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Humankind has been using oil for at least 4,000 years, and oil myths go back just as far. Ancient people believed crude oil had medicinal benefits. Marco Polo, around the turn of the 14th century, discovered camel drivers using it to treat mange. And the first Venezuelan oil export was intended as a gout treatment. In case you thought oil myths were isolated to beauty products and miracle cures, there are plenty of old mechanics’ wives’ tales ready to kill your engine in a few thousand miles.

Myth: Heavy oil is better in summer. Light oil is better in winter.

Fact: Use the oil specified for your year, make and model. With 5W-20, multigrade oil is already heavier in summer and lighter in winter. Thanks to specific oil additives, 5W-20 flows like 5-weight oil when cold and like 20-weight oil when hot. Ambient temperature has very little to do with heat anyway, as engine oil typically runs upwards of 200 degrees Fahrenheit.

Myth: Engine oil lasts forever.

Fact: Engine oil is up to 30% additives added to a base petroleum or synthetic oil, neither of which lasts forever. In the violent engine environment, oil oxidizes and acidifies, leaving deposits. Oil additives oxidize and evaporate, leaving the original oil behind and without additive benefits. Change your oil on time, every time, to keep the system clean and protected.

Myth: Oil is fine if you can’t see or feel any grit or particles.

Fact: Particles as fine as 0.005 inch can’t be detected by hand, but can still damage bearings, especially in newer engines using 5W-20 and 0W-20 oils. Quality oil filters prevent particles from flowing through the engine lubrication system. Replacing the oil filter every oil change prevents overloading, overpressure bypass and unfiltered oil running through the engine.

Myth: You need to change your oil every 3,000 miles.

Fact: Oil change interval depends on vehicle as much as vehicle use. Start with the suggested interval for your year, make and model, then adjust from there. For vehicles with lots of highway miles, the interval may be 5,000, 7,500 or 10,000 miles. For vehicles with lots of city miles, short trips, or towing and hauling, follow the severe service schedule, usually 3,000 or 5,000 miles. It’s a good idea to get an oil change at least annually if you don’t hit the mileage interval.

Myth: Engine oil is a fine replacement for gear oil.
Fact: Because of its lower shear point, engine oil would lead to premature wear in a differential. Engine oil and gear oil lead very different lives. Engine oil simply isn’t heavy enough to protect heavy-duty gear mesh in a differential. The oil additives are also different — gear oil sticks while engine oil flows.

Snake oil is alive and well, and engine oil myths persist without solid basis. Don’t fall for these myths and let your engine suffer the consequences. Always get your oil changed on time, use a quality oil filter and use the oil recommended by the automaker for your specific vehicle.

Check out all the maintenance parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on engine oil myths, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

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