What happens if you put full synthetic oil instead of regular?
John Kim
Updated on March 22, 2026
Answer. Synthetic oils typically provide better protection than conventional oils, but switching back and forth between full synthetic and conventional oil will not damage the engine. Of course, this depends on the current engine condition and the quality of the conventional oil being used.
Can you use synthetic oil after using conventional?
Myth: Once you switch to synthetic oil, you can never switch back. This is one of the most persistent myths about synthetic oil—and completely untrue. You can switch back and forth at any time. In fact, synthetic blends are simply a mixture of synthetic and conventional oils.Will synthetic oil mess up your engine?
Myth #3: Synthetic engine oils can wear down seals in an engine and cause leaks. This is an often-cited myth. In fact, if your seals and gaskets are in good condition, synthetic oil will not leak in your engine. Synthetic oil has not been shown to deteriorate engine seals or gaskets.Will synthetic oil hurt older engines?
It protects better, performs better, and lasts longer, and it's no longer made with a chemical compound that could hurt older vehicles. Modern synthetic oil is safe to use in all types of vehicles, ranging from new purchases to classics to aging not-so-classics.Can I use full synthetic oil on a high mileage car?
High mileage oilSuch oil features additives that help protect seals. This leads to less leakage and oil burn-off, which can be common in older cars. If your vehicle is high-mileage and high performance, it's suggested that you go with this type of synthetic oil.