Can You Mix Motor Oil Brands?

Is it Safe to Mix Oil Brands? Find Out Here

This is a common question; generally speaking, it’s not a good idea to mix different motor oil brands. However, I have to qualify the answer because it depends on how much you’re mixing and under what circumstances. I’ll elaborate more below on when it’s ok to mix motor oil brands and when it’s not a good idea.

Every brand uses a different recipe for its additive package

An oil’s additive package varies from manufacturer to manufacturer, depending on whether the base oil is a Group III or Group IV. Adding a Group III oil to an engine filled with a Group IV oil won’t cause contamination but will reduce the overall lifespan of the oil in your crankcase. In that case, plan on changing your oil ahead of schedule. On the flip side, adding Group IV oil to a crankcase filled with Group III oil may deprive your engine of additives it needs, like viscosity index improvers. Again, it depends on how much you add and under what circumstances.

It’s fine to mix motor oil brands if you’re in an emergency situation

If you’re driving, the oil light comes on and you discover you’re low on oil but can’t find the same brand, it’s ok to mix oil brands. Even the wrong oil is better than low or no oil.

Other than that emergency situation, it’s just not a good idea to mix oil brands due to possible additive interactions from brand to brand.

Other Factors to Consider When Mixing Oil Brands

Viscosity Grade: If you’re going to mix oil brands, at least make sure the added oil is the same viscosity as the oil in the crankcase.

Oil Rating: The current API Service Category is SP. The current ILSAC Standard is GF-6A and GF-6B. If your engine specifies the use of SP, GF-6A or GF-6B, you should not mix brands with a different service category or standard unless it’s an emergency situation. In that case, add the different brand oil, and get your oil change sooner than you normally would.

Oil Type (Conventional vs. Synthetic): Mixing conventional and synthetic oil is technically safe, but adding conventional oil to a crankcase filled with synthetic will dilute the benefits of synthetic oil, such as improved high-temperature performance and better protection against wear. If you’re using synthetic oil, it’s best to stick with synthetic when topping off.

Warranty Considerations: If your vehicle is under warranty, mixing oil brands might be something to avoid. Some manufacturers recommend using specific oil brands or types, and deviating from these recommendations could potentially void your warranty. Always check your warranty terms and follow the manufacturer’s guidelines to avoid any issues.

©, 2021 Rick Muscoplat