Chevy & GMC Vans

I might be buying a safari (from a dealer) that has 120,000 miles on it. Is there some way to tell if the oil in the engine is already full synthetic? When I change the oil, I don't want to go full synthetic if it's dino in there now.

Thanks in advance.

No way to tell unless you send a sample for analysis. Just use dino oil and change it every 3000 miles. Sometimes you can find synthetic on sale cheaper than dino so I have used that.

I used to work fir Valvoline and you can switch between synthetic and non-synthetic oil as much as you want. It will not harm the engine at all. It's just a myth that if you go synthetic that you can't go back.