Do additives work in engine oil?
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Are Engine additives worth using?
There are a lot of aftermarket engine oil additives, such as stop-leak products and oil treatments, on the shelves of your local parts store. These products promise a number of benefits, such as better wear protection, longer oil life, less oil use, higher oil pressure, and better gas mileage. Do these add-ons for engine oil work? Are aftermarket top-treat engine oil additives good or bad?
To find out, we bought two of the most popular engine oil additives on the market and used them to treat a brand-name conventional 5W-30 motor oil. Using tests that are common in the industry, we wanted to see if the additives really did offer the benefits that were claimed. Just scroll down to see what happened.
What are aftermarket treat engine oil additives?
But first, let’s talk about what we mean. What is an additive for top-treat engine oil? How come some drivers use them?
Most engine oil additives are high-viscosity base oils or additives that are added to motor oil to make it better. They are meant to improve the formula in a certain way and give you extra benefits, like better wear protection, less oil use, and so on. Most of the time, they are made and sold to help you fix a problem with your engine, like using too much oil.
Manufacturers of additives keep their recipes secret, which makes it hard to know exactly what you’re buying. However, some additives claim to contain Teflon, molybdenum, or graphite. Some have used chlorine, which is very corrosive when mixed with water, which is often found in oil because of condensation or the way ethanol affects fuel.
Why use a top-treat engine oil additive?
Some drivers who use oil additives do so for good reasons.
Say your car or truck is burning oil. Most likely, the piston rings or valve guides have worn out, letting too much oil into the combustion chamber where it can burn. Rebuilding the engine is expensive and might not be worth it in an old car with a lot of miles on it.
You could go to a mechanic to fix the problem, but wouldn’t you rather buy a cheap additive and cross your fingers that it works?
Or maybe you have a newer car that you want to keep in good shape for a long time. An additive for engine oil that protects against wear better sounds like a great way to make sure your engine lasts for a long time and keeps giving you the power you want. You are doing a little extra for your engine, which is a good thing to do.
Do additives for my engine oil work?
Your goals may be good, but how well does the additive work?
People who use high-quality synthetic oil aren’t likely to add anything extra to it, so we chose to use a conventional 5W-30 motor oil from a well-known brand that can be bought at any auto parts store.
We put conventional motor oil through a few industry-standard bench tests to see how well it protects against wear, flows in cold temperatures, and stays the same viscosity over time. After figuring out how well the oil worked on its own, we added two popular additives to samples of the same conventional oil at the rates listed on their labels. Then we did another test of the oil.
Did the engine additives work?
First of all, our results show that standard oil treated with the two additives we tested did protect against wear better than untreated oil in bench tests.
It came with a price, of course.
Additionally, we discovered that the additives reduced the oil’s cold-flow capability and increased its viscosity to the point where it no longer met the viscosity requirements for a 5W or 30-weight oil.
In the graph below, the orange bar represents the performance of untreated oil in the Cold-Crank Simulator (CCS) Test (ASTM D5293). This test is used to determine an oil’s cold-start fluidity, which helps prevent dry starts and protects against wear. The untreated oil is acceptable for a 5W oil (6,600 cP maximum at -30°C). The comparison also includes the performance of AMSOIL OE 5W-30 Synthetic Motor Oil (the dark blue bar on the left), which demonstrates the enhanced cold-flow characteristics of quality synthetic motor oil.
Consider the performance when using engine additives
Now consider the performance of conventional oil after being treated with engine oil additives in the CCS Test. Both the stop-leak additive and the oil stabilizer increased the viscosity of the oil to such an extent that neither sample meets the requirements for a 5W oil and therefore fails the test. This means that the oil will not flow as freely at startup, reducing wear protection during the period when the most wear occurs.
It’s important to remember that cold-flow isn’t just for those of us who live in the north. Any temperature below your engine’s normal operating temperature, which is about 212°F (100°C), is considered cold. When the engine has been sitting for a long time, like overnight in your garage, the oil will protect against wear better if it flows well. Even though this is especially true at -22°F (-30°C), which is where the CCS Test for 5W oils is done, it is also true at 80°F (17°C) or higher.
This is proven by the cold-pour test shown in this photo. We cooled samples of the regular oil by itself and with the two most popular additives to -40°F.
Take a look at the photo below to see the cold-pour test.
If you use these additives, wear protection and your engine will both get worse over time.
It’s easy to see that the engine oil additives make the oil flow more slowly. When the best oil stabilizer was added, the oil turned into a gooey mass that took about two minutes to move. Imagine putting that oil in your engine, especially if you live somewhere cold. It wouldn’t move when the engine turned on, especially through the small oil passages in the crank journals and camshaft. It also wouldn’t flow through the tiny hole in your variable-valve-timing solenoids, if your engine has them. This would hurt the engine’s performance and might turn on the check-engine light.
How thick is the oil when it's at working temperature?
Even here, the engine oil additives are a cause for concern. In this graph, the orange bar shows how thick the regular oil is at 100°C (212°F) without being treated. The green clear area shows that it is in the right range for a 5W-30 oil.
Now, look at how thick the oil is at 100°C after the two additives were added. That’s right, they are both too thick or too thin. In effect, you are now using a 40- or 50-weight oil instead of the 30-weight oil that the engine manufacturer recommends.
So, what’s so bad about that?
Your engine is made to work with a certain thickness of oil. If the engine’s oil is too thick, it might not move fast enough to fill the space between the crank journals and main bearings, which can cause the bearings to wear out. Thicker oil also makes it harder for the oil to move around, which makes it less able to move heat away from important engine parts. It also makes more heat because there is more friction inside, and it uses more gas.
Is adding engine oil additives good or bad?
You can answer that question yourself based on what you’ve just seen.
Even though they seem to help protect against wear in the short term, the oil additives we tested have major drawbacks that make them less useful in the long run.
You should use a good synthetic oil instead of regular oil to get better wear protection, less oil use, the best fuel economy, and more. Not only will it protect better, but once you add in the cost of the additive, it will cost about the same. And it won’t have the bad effects we’ve already seen.
If you use or are thinking about using an oil additive for your engine, you might want to try AMSOIL OE Synthetic Motor Oil instead. If you are a Preferred Customer, you can save money and could be eligible for free shipping.
Why AMSOIL? Superior protection against wear, improved fuel economy and better performance under extreme temperatures. AMSOIL is the only oil that is able to last up to 25,000 miles. Save yourself time and money and protect your car or truck by using AMSOIL products. Your vehicle will last longer and you will lower your maintenance expenses. Protect your Honda, Toyota, Nissan, Chevrolet, Ford, Chrysler or any other vehicle with AMSOIL synthetic oil!
We advise you to consult your owners manual for proper fluid recommendations and to consult the appropriate repair manual for proper maintenance procedures and specs. Follow all appropriate safety practices. We are not responsible for misuse of products.