From Synthetic Back to Regular Motor Oil
 

What problems might arise switching from synthetic oil back to regular motor oil on a engine with 200,000 miles? A young friend did this and asked me what affects this may have...

Scrapiron66: Iwould not change the formula it has been a succes
to this point, from experience leave well enough alone.
turbo ted

My assumption is that there would be no adverse effect beyond typical effects from regular ("dino") motor oil. Presumably you want to save a few bucks. I don't see a problem. However, you might want to call your favorite oil company and ask them the same question just to be sure.

There are no negative repurcussions when it comes to engine seals and switching off synthetic . Even the Mobil site states you can switch as often as you like .

These better mineral oil formulations have engine seal conditioners " not to be confused with HM oils ' in them now due to the lack of solvency in the better base oils used since around 1999 and these oils pass ASTM tests set by the API and ACEA for engine seal elongation and other parameters .

I used synthetic for a long while, and switched back with no adverse effects. Used Mobil1 and went to Mobil Drive Clean.