Can I switch from synthetic to non-synthetic oil?

August 1, 2010 | By Richard Prince


I have heard rumors that it is detrimental to switch from synthetic engine oil to non-synthetic. Or is this all a myth and switching from synthetic to non-synthetic is actually harmless?

The bottom line is that I’m tired of putting $6-a-quart oil into my 1993 Mercury Grand Marquis just because the guy I got it from had synthetic in it. In addition, it uses some oil so the oil added between changes is costing me too.

As a result, I’m doing a bad thing— I’m stretching out the oil change intervals to past where I would normally change the oil if it wasn’t so expensive. So whatever good there is in using synthetic oil is probably offset by my efforts to avoid its added costs.

This is a second car for me that isn’t driven much so efficiency and wear issues are not a big factor.

What can you advise me about switching off of the synthetic oil?


The added cost of synthetic oil is normally offset by its dramatically increased longevity, but if you’re not comfortable changing the oil every 7500 or 10,000 miles then the added lifespan of the costlier oil doesn’t help you much. And if your car is burning a significant amount of oil between changes that obviously alters the calculation as well.

Switching from synthetic oil to non-synthetic oil in an engine that was designed to run with non-synthetic in the first place will do no harm at all.

Switching the other way, from non-synthetic to synthetic oil in an engine that was not designed to run with synthetic, especially an older, high-mileage example, can lead to numerous problems, especially leaks.