Using Oil Additives for High Mileage Engines:Do They Really Work?

As engines age and accumulate miles, they can begin to show signs of wear and tear, resulting in decreased performance and efficiency. To combat this, many car owners turn to oil additives specifically designed for high mileage engines, claiming to rejuvenate and protect their vehicle’s engine.

These additives typically contain friction modifiers, detergents, and other ingredients that claim to reduce wear, improve fuel economy, and increase horsepower.

But can anyone really claim they know for sure that any of these additives do actually help, and more specifically do they help for high mileage driving?

Understanding High Mileage Engines

When we are talking about high mileage engines here, we’re speaking about cars that have at least 75,000 miles or more on them. And it doesn’t matter if they are city miles or open road miles, as far as numbers, we’re just giving you an idea here.

And the reason is most mechanics agree that 75,000 or more miles is when things start to show wear and it starts getting even more important to do your regular maintenance routines, especially oil changes.

This is because every time you use your car you do indeed pace stress on the engine as far as it is firing and moving, and although each time you use it may only wear down the engine the tiniest bit, this all accumulates over time. And of course the longer and more times you use your car, the more wear and tear you put on it.

This is the same whether the car is 20 years old or it’s only two months old, mileage equals wear and tear on your engine’s internal parts regardless.

And although you can never completely stop the wear on your car, you can help minimize the harmful effects so that your engine lasts a bit longer and you have fewer maintenance issues by using oil additives.

Types of Oil Additives for High Mileage Engines

So what are the best types of oil additives that are being marketed right now for high mileage engines specifically?

Detergents and dispersants: These help keep your engine clean by preventing dirt buildup. They also keep impurities suspended until your next oil change.

Viscosity improvers: Viscosity just means how thick or thin a liquid is due to temperature changes and age. Your oil is a liquid and therefore the thickness of it changes depending on environmental forces and its age. Viscosity Improvers work to make sure your oil is always at the best thickness so it can do its job correctly.

Friction modifiers: Friction is one of the worst things for a car’s engine as this is what creates the most wear on its internal parts. Many oil additives contain friction modifiers to try and reduce the amount of friction going on inside.

Seal conditioners: All engines have seals that are made of rubber inside their engines. These seals need to stay pliable so they don’t get brittle and crack, then they’d need to be replaced. Seal conditioners are like a shampoo conditioner for your car’s seals keeping them soft and pliable.

Anti-wear agents: Like I wrote before, wear is what makes an engine break down and is just a natural cycle in an engine’s life. Anti-wear agents do their best to slow down wear by adding a thin layer like Teflon does on cookware to make it non-stick.

Corrosion inhibitors: Designed to protect your engine from corrosion and rust. Moisture and oxidation are common issues in high-mileage engines.

Rust preventers: Similar to corrosion inhibitors, but they are specifically designed to prevent rust from developing on engine parts.

Extreme pressure additives: These oil additives help protect your engine from extreme pressure and heat. Basically they form a protective barrier that can withstand high temperatures and pressure.

Do Oil Additives for High Mileage Engines Really Work?

Manufacturers of oil additives for high mileage engines often make a variety of different claims regarding the benefits of their products, some true and some not so true.

So there’s a lot of debate when it comes to the effectiveness of oil additives in high-mileage engines. Additive manufacturers will claim that their products deliver extreme results but buyer beware. They claim to improve fuel economy, reduce engine noise, increase engine power, and extend engine life, but do they? Studies have shown that oil additives are not always as effective as promoted. In some tests, they were noticeably effective whereas in others, they are not. The results varied greatly depending on the specific additive and the type of engine being used.

One such study was conducted by the Fuel Economy Improvement Committee of the Society of Automotive Engineers (SAE) which claims that oil additives could indeed improve mileage although the effectiveness was highly dependent on the driving conditions and the engine’s design.

In a different study, the American Society for Testing and Materials (ASTM) found that some oil additives could be effective at reducing wear to the engine’s internal parts, but again, with the stipulation that it depended a lot on the specific additive and the type of engine it was used in.

With such varying results, it’s hard to say which oil additive will be effective and which will not. It appears to depend on the additive being used, the type of engine, and the driving conditions. Do your research and choose an additive that has a proven track record of effectiveness in similar engines and conditions as yours.

Risks and Drawbacks of Using Oil Additives

Like everything, there are always potential drawbacks to using any sort of additive in your car’s engine.

Potential damage to the engine: As with any product you use, if you don’t really understand the product or what it’s doing exactly there’s always the possibility your using it wrong or you’re using the wrong product for the wrong application.

Negative effects on the oil: Some oil additives can actually affect the performance of your engine oil in negative ways. Oil additives could possibly harm your oil making it unable to lubricate effectively or even cause the oil to break down more quickly.

Compromised viscosity index improvers: Some oil additives can interfere with viscosity index improvers aimed to adjust oil viscosity according to engine temperature.

Check with your vehicle’s manufacturer to see which oils and additives they recommend. Not all additives are safe and appropriate for your vehicle and at times, if used incorrectly can even affect your vehicle’s warranties.

Always do your own research as far as what brands are nationally recognized and manufacture their products according to the newest safety guidelines.

Try to figure out what problems are according to what it is specifically you’re trying to remedy with these additives and then look for the right one to use.

And always read the manufacturer’s instructions to see how much you should be using and to see if there are any safety risks for your particular car manufacturer or model.


So to wrap up, the use of oil additives for high mileage engines remains a contentious topic in the automotive industry for a variety of reason I wrote about above While some studies we’ve written about above have shown that these additives can help improve engine performance and extend engine life, the results vary depending on the specific additive, type of engine, and driving conditions.

Furthermore, some additives may have risks and drawbacks, such as clogging the engine or causing more harm than good. It is important to do thorough research before using any oil additive and to choose one that has a proven track record of effectiveness in similar engines and conditions as yours.

Regular maintenance, including oil changes, remains the most effective way to keep your engine running smoothly and prevent costly repairs.


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