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Extended Oil Change Drain Intervals--Are They Safe?

American Government Special Collections Reference Desk

Extended Oil Change Drain Intervals--Are They Safe?

Steve Tarini
1 December 2009


Making Sense Of Oil Drain Intervals

It is becoming more and more common for both oil and car manufacturers to suggest going well beyond the old 3,000 mile drain interval that used to be considered good practice. People are always skeptical of change, however, especially when the information is so very conflicting. How is one to know who is right? Let's take a look at the facts so that you can decide for yourself.

Why We Change Motor Oil

It would help to understand why we change motor oil at all. Motor oil is responsible for several things including lubricating critical engine parts and to a certain extent, cooling the motor. As the oil heats up and cools down repeatedly, and as the rubber seals absorb the chemicals that they are intended to absorb, the additives are pulled out of the oil. As moisture settles into the motor oil, it's viscosity, or ability to provide lubrication, begins to diminish. Thus motor oil can be "worn out", so to speak.

How Oil Manufacturers Decide How Often The Oil Should Be Changed

The most logical, and most honest way to determine how often motor oil should be changed should be based on the oil's ability to do its job: condition the seals and lubricate the engine. One company in particular suggests drain intervals of 25,000 miles. That means this oil can resist the day to day punishment and still effectively lubricate critical engine parts and provide the additives to keep your seals healthy for at least that long.

How Oil Manufacturers Make Extra Money

There are some companies, however, who seem to take a less scrupulous and more money grubbing approach at dictating drain intervals. Some of the major brands that offer 15,000 miles drain intervals suggest changing the motor oil at the manufacturer's suggested intervals until the car is no longer covered by a warranty. Then they suggest going the full 15,000 miles that their product offers. This is rather silly, and no mechanic in his right mind would tell you that your oil drain intervals should increase as your car gets older. If anything, the drain intervals should be shorter on older vehicles, assuming that inferior or questionable motor oil was used at some point. If it's okay to go 15,000 miles after the car has 36,000, 60,000, or even 100,000 miles on it, it stands to reason that those same drain intervals would be suitable from the time your car is brand new and still under warranty.

It's Federal Law as dictated by the Magnusson Moss Act for the car manufacturer to void your warranty for using oil with longer drain intervals unless they provide both the oil and the labor to change it, free of charge, so the warranty is not at issue. If the motor oil is capable of protecting your car for longer, than your car does not benefit from changing it more often. You, who has to pay for the oil, certainly do not benefit from spending more money. The oil manufacturers, however, can look forward to a steady income from people who obviously can afford to buy new cars, while at the same time selling their oil to those who are more frugal and keep their cars out of warranty.

There is nothing stopping you from going well past 3,000 miles on any motor oil that offers extended drain intervals right from the beginning. Or, if you're really looking to save some money, you could go with the oil that recommends 25,000 mile intervals, regardless of the vehicle's mileage and warranty status.


Author-Steve Tarini specializes in the testing and marketing of Amsoil Synthetic Lubricants. Amsoil has offered extended drain intervals longer than any other oil manufacturer and that includes both Mobil 1 and Castrol. In less than 5 years the 3,000 mile interval will be a history because synthetic lubricants have evolved so far. Compare Amsoil vs. Casrtol vs. Mobil and see what you think.

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