Oil additives are marketed as useful products to splash into your engine, claiming to decrease wear, extend the life of your oil, and clean out harmful deposits. But according to a series of laboratory tests and real-world analysis, oil additives have the potential to do far more harm than good.
The Motor Oil Geek on YouTube set out on a fact-finding discovery to see whether the most popular oil additives on the market are any good at helping out the health of your engine. Host Lake Speed Jr. spent 12 years as Joe Gibbs Racing's lubricant specialist, so if anyone knows how oil works, it's him.
Speed Jr. picked out nine oil additive products you can find on the shelves of any auto parts store for this test. Stuff like Marvel Mystery Oil, Lucas Stabilizer, Rislone ZDDP Supplement, and Seafoam oil treatment are all extremely popular, but according to this test, you're better off leaving them out of your engine's oil.
It's important to understand motor oil is already a very complex, precisely formulated mixture. It's designed in a lab by a team of engineers who created it to perform under a specific set of circumstances. Throwing an additive to the mix, no matter how well-formulated, will always interfere with the base oil's properties. The result is, according to Speed Jr., is a shorter oil lifespan and possibly more wear.
"If you have to put an additive in your oil, you have the wrong oil," he says.
In an oxidation test, Speed Jr. discovers that both Lucas Stabilizer and Marvel Mystery Oil increase the viscosity of the oil and cause imbalances in the mixture, decreasing the oil's effectiveness. In a separate test, he discovers Seafoam pulls in water from the atmosphere (the presence of water in an engine is bad) and actually boils away before the engine reaches operating temperature.
Oil Extreme, another additive, is especially dangerous for direct-injection motors, Speed Jr. says. The high amounts of calcium and sodium present can actually cause low-speed pre-ignition, giving it the potential to cause serious damage. The Rislone supplement is also bad, Speed Jr. says, because it raises the acidity of the oil, opening up the engine to corrosion-based damage and excess bearing wear.
In short, Speed Jr. says you should stay away from oil additives and instead choose the correct base oil for your engine.
"It's basically chemical Russian roulette whenever you add an additive to your oil," he says.
While oil additives are bad, you shouldn't discount fuel additives, according to Speed Jr. Every major-brand fuel additive contains a chemical called polyetheramine, a detergent that cleans injectors and removes combustion chamber deposits. Cleaning out injectors means better atomization of the fuel during the combustion process, which results in more power and more efficiency. So if you want to improve the health of your engine, start with the fuel system, not the oil.
