Can you mix different types of engine oil?
THE STARTER - Lord Seno (The Freeman) - June 25, 2018 - 12:00am

Your engine oil warning light turns ON and you drive to a gas station. The mechanic puts in regular oil in your engine. You go home and tell your  husband about the oil adding when he tells you he did a full synthetic oil change and not the regular.So goes the question, did you make a mistake in adding regular oil to synthetic?

Mixing  Synthetic, Semi Synthetic and Mineral (Regular) Oils

The answer is yes.  I have been guilty of doing this a few times, some during emergencies.  None of my engines seized or blew-up! Engine oils, whether the regular /conventional or the synthetic, has compatible base oils and additives.  It would be unlikely anything bad would happen, such as a gel-forming from an interaction of the chemicals.  In fact, many oils are a blend of natural and synthetic oils. Synthetic oils are of much higher quality because they are manufactured using a tedious process that removes a lot of impurities inherent to regular engine oil. Synthetic oils also contain better quality additives.While you can safely mix synthetic and regular oils, you're doing nothing more than diluting the performance of the synthetic oil.

Possible Adverse Effects of mixing Engine Oil

Synthetic oil is expensive because it does a great job of lubricating and cleaning your engine. Regular ones are cheap because they can only do so much.  If you mix both,  you'll 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's possible it will be displeased with the mix of regular and synthetic.   Short term damage to your engine will be unlikely, but there will always be adverse long term effects, plus it won't help the engines performance.

The Difference Between Regular and Synthetic Oil

Both conventional and synthetic motor oil is derived from petroleum, the mineral that they pump out of our earth.  These two may be similar and compatible but they can be very different products based on how they do their jobs! 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 runs through multiple steps in its refinement.  It is also distilled and purified so that it contains fewer impurities.  Synthetic oil is processed to have a smaller set of molecules to peer through the tight clearances on the moving parts of the engine, thereby offering better engine protection.  These types of oil also contain additives intended to help keep an engine cleaner and protect it from damage.

The big difference between regular and synthetic oil is the temperature tolerance before thermal  or heat degradation. In a high-performance engine, regular oil is more susceptible to heat degradation,  sludge forming  and  dirt build up. 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.

So, if you made that mistake of mixing it, that's okay.  If you are low on oil, don't be afraid to add a quart or two of synthetic or regular oil. You don't need to rush right out and get an oil change so you'll have a uniform blend of oil in your engine.  But make sure to do the oil change intervals for the regular oil instead of the longer synthetic oil change interval.

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