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High Mileage Oils--Are They Really Worth The Extra Cost

American Government Special Collections Reference Desk

High Mileage Oils--Are They Really Worth The Extra Cost

Steve Tarini
25 November 2009

What Is High Mileage Oil?

High mileage motor oil is generally a synthetic blend with additional additives to "recondition" your seals. I use the term recondition rather loosely because it's based on the assumption that the seals in your engine are in bad shape, which is not always the case. They also generally include an additive that prohibits the oil from burning off if it does get past the presumably leaky seals.

How Do These Additives Work?

That is a very good question. Unfortunately, there is no readily available answer. There are many theories floating about but, with the exception of whoever does the actual designing and blending of the oils, no one seems to know, and those guys aren't telling. It's not even clear exactly what it is they are adding to the motor oils to perform these tasks.

How Does One Know If Their Car Needs High Mileage Oil?

According to the oil manufacturers, it is generally suggested that you use high mileage oil in any car with an engine that has over 75,000 miles on it. This claim is interesting for a few reasons. For one thing, it's an oddly concrete number considering car manufacturers vary widely on how often you should change your engine's oil. If you look at the directions on the bottles of the few manufacturer's that say how often you should change your oil, they almost always tell you to refer to the owner's manual. Excellent idea. Remember, the owner's manual tells you how often you need to change your oil using the minimum quality oil that is recommended. You should never be using anything less than that, anyway. Most modern owner's manuals go up to 200,000 miles. So, at what point does your owner's manual say to begin using "high mileage" oil. I'm betting it doesn't.


The consumer is faced with making a decision using very little facts. The oil companies don't tell us why they figure a high mileage engine needs different oil, and they don't tell us how it does what it does so that we can draw our own conclusions. All we have to go off of is that they say to use high mileage oil after 75,000 miles. However, that flies in the face of their recommendations to change the oil at the intervals suggested by the manufacturers. So either the oil companies feel that the manufacturer's schedule is not adequate, which begs the question of why are they not telling us what is adequate to keep this so called seal damage from occurring in the first place, or they're just hoping we'll take their word for it and unquestioningly spend the extra money on the "high mileage" version of the same oil that they claim was already doing a good job of keeping your seals in good shape.

Steve Tarini is an accomplished expert in the field of extended drain intervals and synthetic lubrication. There is an equaly important article on my website discussing the pro's and con's of High Mileage Oils. Don't be fooled by the marketing, you're better off starting out with a high quality synthetic oil and get the most life out of your car. Check out this article on High Mileage Oils

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