Informational Guide

Can You Mix Synthetic Oil With Regular Oil

You know the differences between the oil types, but you might not understand how each works. Can you mix synthetic oil with regular oil if you need to top off the system?  

In this article, we discuss mixing synthetic oil with regular oil and show you if it's ok to do.  

Can I mix synthetic oil with regular oil? Before you decide if this is ok, you must first understand the two kinds of oil. Regular or conventional oil is the most basic type. It is the refined natural form of motor oil and has been the standard for many decades. These days, you find the regular oil in older vehicles, and it's often chosen to save money during an oil change. However, it needs to be changed more frequently because it gets contaminated quicker. 

Synthetic oil has been formulated by man with special additives and detergents to extend its life. For this reason, it doesn’t need to be changed as quickly. Plus, it helps to clean out the engine for a longer life. One big downside is the price. Synthetic oil is much more expensive than conventional oil, but it doesn’t need to be changed as frequently.  

For this reason, some people choose to use a synthetic blend, which has properties of synthetic oil and conventional types. But, because a synthetic blend is the combination of both, can you mix regular oil with synthetic on your own? 

understanding motor oil

Can Synthetic Oil And Regular Oil Be Mixed? (Is It ok To Do?) 

Is it ok to mix synthetic oil with regular oil? The technical answer is yes. The two oils can be mixed together. For example, if you are topping off the engine and only have the opposite oil available, you won’t hurt anything by adding it to the system. However, you need to make sure that the two oils contain the same viscosity as outlined in your car owner’s manual. 

Is it safe to mix synthetic to regular oil? If it is done occasionally, there should be no harm to the engine. What about high-mileage oil? Can you mix high mileage synthetic oil with regular? As long as the viscosity is the same, there should be no problems.  

It’s important to note that mixing full synthetic with regular oil doesn’t create a blend comparable to what you can purchase in the store. The synthetic blend is specifically designed to a particular combination that will work in your car engine. 

can synthetic and regular oil be mixed

With that said, most motor oils are compatible with others, as long as the viscosity is the same.  

Is it bad to mix synthetic oil with regular? Not necessarily, but there are some reasons you might want to avoid this practice.  

What Happens When You Mix Synthetic And Regular Oil? 

Can you mix full synthetic oil with regular oil? While you can, you need to consider the ramifications of this choice. What happens if you mix synthetic oil with regular oil? There won’t be any dangerous consequences, but you won’t get the effect you are hoping for. 

Let’s say you add regular oil to your synthetic oil just to top it off. By doing this, you just decreased the effectiveness of the higher-priced synthetic oil. You might even need to get an oil change sooner because it could be contaminated prematurely. It seems silly to spend more on synthetic oil changes when you decrease its lifespan. 

Can synthetic oil mix with regular oil? You could put synthetic oil into the regular oil, but this doesn’t extend the lifespan. You will still need to get an oil change at the regular interval. Basically, you just poured more expensive oil into the system when you didn’t need to. You could have saved money and put more conventional oil into the engine until you get an oil change.  

mixed synthetic and regular oil

People Also Ask (FAQs)

Can you switch from regular to synthetic?  

You can switch between the two at any oil change. Feel free to make the change with each oil service if you want. Mixing a small amount of residual conventional or synthetic oil with the opposite won’t affect anything.  

Can you mix synthetic oil and regular oil in a motorcycle? 

Mixing synthetic oil with regular won’t hurt anything in your motorcycle. However, it might cause you to need an oil change sooner, depending on what you have mixed.  

How often should synthetic oil be changed? 

On average, synthetic oil gets changed every 7,500 to 10,000 miles. With the synthetic oil, you want to use an oil filter that can go that long between engine service.  

How often should regular oil be changed? 

It’s recommended to change conventional oil and filters every 3,000 to 5,000 miles. If you have an older engine or it has a lot of miles, you might want to change the oil more frequently.  


Can you mix synthetic blend oil with regular oil? You have nothing to worry about, whether you accidentally mixed synthetic oil with regular or you need to do so in a pinch. Just watch the viscosity of the oils you are mixing.