There are two schools of thought about using high-mileage oils. The first is to switch when your vehicle reaches 75,000 miles. The second is to switch if your older vehicle is beginning to show signs of engine loosening. If you notice an oil drip, that’s a sign you should start using high-mileage engine oil. If your engine “sounds louder” and you are noticing a new rattling noise, sometimes the engine would benefit from a denser oil.
If you’re not having any issues, don’t change your engine oil. Because high-mileage oils are usually not API licensed, I recommend waiting until your vehicle’s warranty period is over before considering switching.
What Exactly Is High Mileage Oil?
As the name implies, this type of motor oil is formulated to address the specific problems encountered by high mileage vehicles, or those with more than 75,000 miles. It can help reduce oil consumption, smoke, and emissions from older engines. High mileage oil also works to minimize leaks and oil seepage.
While you could use high mileage oil in a younger car without harming it, the issues that high mileage oil addresses usually don’t appear in vehicles with fewer than 75,000 miles.
How Does High Mileage Oil Work?
High mileage oil works as a powerful multivitamin, restoring worn engine parts and preventing further wear and tear.
As the seal conditioners within high mileage oil expand and rejuvenate seals, less oil seeps out from your engine. This results in less oil consumption, which means fewer oil changes and fewer engine problems down the road.
High mileage oils also contain various antioxidants, detergents, and additives to decrease wear and friction—all things that are advantageous for engines past their prime. These ingredients clean out the grime and sludge that naturally builds up over time, while simultaneously minimizing friction so your engine purrs like a kitten.
Who Needs High Mileage Oil?
Cars with more than 75,000 on their odometer can usually benefit from high mileage oil. Older vehicles with fewer miles can benefit too, as engine seals can erode over time regardless of mileage. Degraded seals mean leaking oil, and leaking oil means your engine isn’t working at its best.
You might want to switch to high mileage oil if:
- You back your car out of the garage and find oil stains on the ground where your car was parked. Oil drips could indicate a loosening of engine parts.
- You look under the hood and notice oil streaks on lower engine parts.
- Your engine sounds louder than normal. A rattling noise might signal that your engine could benefit from denser motor oil, i.e., high mileage oil.
- If you’re committed to preserving your vehicle for the long run, stick to regularly scheduled preventative maintenance services, especially oil changes with high mileage oil.
How Does My Engine Benefit from High Mileage Oil?
High mileage oil addresses specific weaknesses in your engine that are related to old age. It’s like a healing ointment for overused engine parts.
- Reduced oil consumption: High mileage vehicles tend to leak and burn off more oil than younger cars due to degraded engine seals. High mileage oil rejuvenates degraded seals, which leads to less oil consumption and burn-off.
- Less engine sludge: older engines tend to accumulate sludge left behind by other motor oils. High mileage oil breaks up and dissolves residual sludge.
- Protection from damage: High mileage vehicles tend to suffer from more general wear and tear than younger cars. The additives in high mileage oil preserve and protect your entire engine.
What Is Considered High Mileage?
When oil manufacturers refer to “high mileage cars,” they are usually referring to cars with 75,000 miles or more on the odometer.
High Mileage Oil vs. Regular Oil
High mileage oil contains special antioxidants, detergents, and additives that can help reduce engine wear and minimize the chances of sludge buildup.
Importantly, high mileage oil helps prevent aging seals and gaskets from becoming brittle and causing leaks, which are usually evidenced by oil stains on the pavement where the car is parked. This can lead to increased oil consumption and even costly engine damage.
High Mileage Oil vs. Synthetic Oil
High mileage oils are usually synthetic oils. They are typically based on either full-synthetic oil or a blend of synthetic and conventional oil. Synthetic oil offers greater protection in extremely high temperatures, and its ability to flow without difficulty in cold weather helps make engine starts easier in freezing weather. Whether full or partially synthetic, high mileage oil is more expensive than standard grade oil.
High mileage synthetic or synthetic blend oil, as with the conventional variety, is available in various weights that are labeled according to their viscosity, a measurement of an oil’s thickness or resistance to flow.
This is expressed as a series of numbers, such as 10W-30. The lower the first digit, the more resistant the lubricant will be to thickening in low ambient temperatures (the “W” stands for winter). A higher second number means it provides added protection against thinning when the weather turns hot. Check the owner’s manual to see what’s recommended for your vehicle based on how and when it’s driven.
So, Is High Mileage Oil Worth the Money?
Though it provides an added layer of protection for older cars, some sources suggest a specific high mileage blend might not be worth the extra money if a car’s engine is not already leaking or is burning oil excessively. If that’s the case, choosing a higher viscosity (thicker) grade conventional oil and/or using stop-leak additives to bolster seals can be a lower-cost alternative.
Check an Older Car’s Oil Once a Month
To further help extend the life of an older car, truck, or SUV’s engine, drivers should check the oil level at least once a month between changes, since extended driving with a low oil level could lead to engine damage.
If your car needs more oil, follow the instructions provided in the owner’s manual. Add a quart of oil when the level indicated by your engine’s dipstick reaches or drops below the “ADD” marking.
Can You Mix High Mileage Oil and Regular Oil?
Despite what some drivers may believe, if the need arises, you can mix high mileage motor oil with the conventional or synthetic variety (or vice versa) in your car’s crankcase, though you’ll lose some of the benefits of the high mileage oil in the process. You can also switch back and forth from one type to another at subsequent oil changes without fear of engine damage.