You know that proper oil changes are crucial to the health of your engine. But at some point during your vehicle ownership, whether out of curiosity or necessity, you might ask, “Can conventional and synthetic oil be mixed?" The short answer is yes, but it’s typically not ideal.
Read on to learn how mixing oil types can affect the end product’s characteristics, and what that might mean for your engine.
What Happens When You Mix Synthetic and Conventional Oil
Despite popular engine oil myths, mixing synthetic and regular oil (regular meaning conventional) will not harm your engine—provided they are both the correct viscosity and meet the correct performance and quality specifications set by your vehicle’s manufacturer. However, there are very rare exceptions, such as some older Mazda rotary engines that prohibited synthetic oils, so always check with your owner’s manual first.
Synthetic oil is engineered to be the best it can be—to perform under extreme temperatures, keep your engine cleaner, and provide enhanced engine protection and lubrication. This superiority can be costly, though. Alternatively, conventional oil may not perform quite as well in these areas, but it can offer reliable performance at a lower cost. The key is to ensure that only oils that are of the correct viscosity and meet the correct performance/quality specifications are used.
A Note on Topping Off Engine Oil
Many wonder if they can mix different types of oil because they need to “top off” their engine oil. While topping off your oil can be a temporary fix for low engine oil levels, it’s important to remember it should be just that — temporary. Topping off your oil is not a substitute for proper oil changes, since pre-existing oil in your engine reduces the effectiveness of the newly added oil.
Additionally, if you frequently have to top off your oil, it could be a sign of an underlying issue. Between oil changes, your engine oil level should stay relatively stable. If it doesn’t, it could indicate a leak or excessive oil consumption, which should be addressed by a professional.
Oil Mixing FAQ
Can You Mix Synthetic Blend Oil With Regular Oil?
As with full synthetic oils, you could mix synthetic blend with regular in a pinch, but that doesn’t mean you should. If you choose to do so, each oil must meet the specifications set by your vehicle’s manufacturer.
Can You Mix Synthetic and Synthetic Blend Oil?
As long as both the synthetic oil and synthetic blend oil have the correct viscosity and meet the performance and quality specifications required by your vehicle’s manufacturer, this shouldn't pose a risk to your vehicle.
Can You Mix Engine Oil Brands?
Engine oil brands that abide by your vehicle manufacturer's specifications should be compatible, and mixing them should not be a problem. However, sticking with one brand will ensure compatibility.
Can You Mix Engine Oil Weights?
Mixing oil weights can affect viscosity levels and cause damage to your engine. This is not recommended.
To properly reduce friction and wear, engines are designed with a specific oil weight in mind. Oil weights refer to the oil’s viscosity at different temperatures. The weight of an engine oil is denoted by two numbers, like 10W-30. The first number (followed by a “W”) indicates the oil’s viscosity at cold temperatures, while the second number refers to its viscosity at engine operating temperatures.
Since mixing oil weights can result in an unpredictable final viscosity, we strongly recommend only using your vehicle’s manufacturer-recommended oil weight. Anything else could negatively impact your engine’s longevity and performance.
Need an Oil Change? Firestone Complete Auto Care Can Help
When it comes to mixing oils, it is always best to adhere to your vehicle’s manufacturer's recommendations.
Fortunately, taking care of your engine doesn’t have to be difficult; Firestone Complete Auto Care offers comprehensive oil change services so that you can ensure your oil is changed and disposed of properly by our experienced technicians. To ensure the best results and longevity of your engine, stop by your nearest store or schedule an appointment online today.
