Sappasit Wongkhonkan/EyeEm/Getty Images Updated on January 10, 2020 Here's a practical chemistry question for you: Do you know what happens if you mix regular and synthetic motor oil?
Let's say the mechanic put synthetic oil in your car when you got your oil changed. You stop at a gas station and see you are running about a quart low, but all you can get is conventional motor oil. Is it all right to use the regular oil or will you risk harming your engine by doing so? According to Mobil Oil, it should be fine to mix oils. This manufacturer states it would be unlikely anything bad would happen, such as a gel-forming from an interaction of the chemicals (a common fear), because the oils are compatible with each other. Mixing Motor Oil
Many oils are a blend of natural and synthetic oils. So, if you are low on oil, don't be afraid to add a quart or two of synthetic oil if you are using regular oil or even regular oil if you are using a synthetic. You don't need to rush right out and get an oil change so you'll have "pure" oil.
Possible Negative Effects
It is not recommended to routinely mix oils because the additives in different products may interact or the oils may become destabilized by the mixture. You may reduce or negate the properties of the additives.
You could lose the benefits of the more expensive synthetic oil. So, adding regular oil to your special synthetic oil will mean you'll need to get your oil changed sooner than you would have otherwise.
If you have a high-performance engine, it may not allow the (expensive) additives to work the way they are supposed to. This may not damage your engine, but it won't help its performance.
Difference in Regular and Synthetic Oil
Both conventional and synthetic motor oils are derived from petroleum, but they can be very different products. Conventional oil is refined from crude oil. It circulates through the engine to keep it cool and prevent wear by acting as a lubricant. It helps prevent corrosion, keeps surfaces clean, and seals the engine. Synthetic oil serves the same purpose, but it's tailored for higher temperature and pressure.
Synthetic oil is also refined, but then it's distilled and purified so that it contains fewer impurities and a smaller, select set of molecules. Synthetic oil also contains additives intended to help keep an engine cleaner and protect it from damage.
The main difference between regular and synthetic oil is the temperature at which it undergoes thermal degradation. In a high-performance engine, regular oil is more apt to pick up deposits and form sludge.
Cars that run hot do better with synthetic oil. For most automobiles, the only real difference you'll see is that synthetic costs more initially but lasts longer between oil changes.
The simple answer: Yes. There is no danger mixing synthetic and conventional oil in your engine. However, conventional oil will detract from the superior performance of synthetic oil and reduce its benefits.
The detailed answer: With synthetic engine oils continuing to grow in popularity, the question of whether synthetic and conventional oils can be safely mixed often arises. I am guilty of having mixed different types of engine oil with reckless abandon back in the day. A dash of synthetic blend to top-off my car one month and a shot of cheap conventional oil the next.
Although I’m sure performance suffered, my engine never blew up as a result. So, yes, you can safely mix synthetic and conventional oil. But barring an emergency, it’s not a great idea.
Compatible components
All engine oil, whether synthetic or conventional, is a combination of base oils and additives. Synthetic base oils are manufactured using a process that removes the impurities inherent to conventional base oils and typically contain higher-quality additives. All in all, conventional and synthetic oils are comprised of the same, compatible components – it’s just that the components in synthetics are of a considerably higher quality. While you can safely mix synthetic and conventional oils, you’re doing nothing more than diluting the performance of the synthetic oil.
You may not have a choice in some cases. If you’re travelling, for example, and suddenly find your engine low on oil, cheap conventional oil may be the only option at the petrol station alongside the motorway. While it’s safe to top-off an engine that normally uses AMSOIL synthetic engine oil with conventional oil, we recommend changing the oil at your earliest convenience. In fact, AMSOIL does not support extended drain intervals where oils have been mixed.
When you’re using the best oil available, why add anything to it?
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