Rick's Free Auto Repair Advice

High mileage oil

What’s the deal with high mileage oil and high mileage oil filters

People always ask me if they should buy high mileage oil. Here’s my take on it.

This article is just one in a series. If you’d like to know more about oil click on the links below.

Choosing the right motor oil

Chrysler’s 3.5-liter engine has oil sludge issues

High mileage oil and oil filters

Oil Viscosity Warning

Synthetic Oil Facts and Myths

Synthetic oil versus conventional oil

What motor oil to use

What oil brand is best

What oil should you use

When to change oil

Best Oil filter

What is high mileage oil?

All engines (even new ones) have some amount of blow-by. That’s combustion gas that squeezes past the piston rings and into the crankcase. Because high mileage engines have more cylinder and ring wear, they also have higher rates of blow-by gasses. Blow-by gasses contain unburned fuel, acids, water and soot. So you’re literally blowing trash into the crankcase. It’s the oil’s job to take out the trash and the additives in high mileage oil help it do its job.

Oil is made up of 25% additives. Those additives contain anti-corrosion chemicals, anti-foaming agents, anti-wear compounds (mostly zinc), dispersants and acid neutralizers. High mileage oil has a higher percentage of anti-corrosion, anti-wear, and acid neutralizers than traditional oil. Older engines need that extra protection because the blow-by and wider clearances create more heat and oxidation which wears out the additives faster.

Valvoline MAX life high mileage synthetic blend oil and Valvoline MAX Life high mileage full synthetic oil

High mileage oil is available as a synthetic blend or full synthetic. Full synthetic high mileage oil provides the best protection for older engines

In addition to those additives, high mileage oils also contain seal swell agents to soften aged seals.  Nitrile seals get brittle and crack as they age and heat takes its toll. Seal conditioners soften the Nitrile seals and make them more pliable. That means fewer leaks from seals.

Check your dipstick more often as your engine ages

Older engines tend to burn and leak more oil. Running your engine when it’s even a quart low can dramatically reduce the life of the remaining oil. If you’re accustomed to changing your oil every 7,500 miles but run your engine a quart low, you could wear out the critical additives in your oil as soon as 5,000 miles.

Read this frightening statistic from oil industry publication Lubes and Greases

“If an engine becomes starved for oil, it can suffer premature wear and even failure. Fast oil change outlets have reported servicing vehicles with upwards of 10,000 miles since the last oil change that are two to three quarts low on oil. Oil that is used significantly beyond its prescribed drain interval can
become heavily oxidized and too viscous to drain from the engine, let alone lubricate it effectively.”

Lubes and Greases, March 2017

© 2012 Rick Muscoplat

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Posted on by Rick Muscoplat



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