acutaly, if the car has significant mileage on synthetic, switching to dino oil could cause enough shock to the seals that it could cause the engine to leak from multiple places. This is because the conditioners and detergents in synthetics are of a much higher grade and when you remove those all of a sudden, it causes the seals to shrink and leak. If you wantto use conventional, use a 50/50 blend for two changes or so, to prevent or ease the transistion.Synthetic oil is fine and keeps the engine clean but it will not harm a car to use dino oil. I use dino oil and have never experienced any problems using it. I keep some cars as long as 10 years and never an engine failure. I tried synthetic oil in my Tacoma pickup and switched back to dino oil because there was no noticeable difference in engine performance or fuel mileage. It is OK to switch from synthetic oil back to dino oil. Synthetic blend is probably a waste of money.
Clifton
...seriously how many synthetic oil threads do we really need.