Just went in and had my 52500 service done. When I got home I found out they put Penzoil in my car. Icall them back and they said they never put synthetic oil in a 08 G. Went back through all my service history sheets and every one except Prestige of Tallahassee used syn on my car. Either Castroil or Ester. I am taking it back this afternoon and they will change it oput to Ester for me, but I'm wondering if there are any ramifications swapping back and forth.

 

not really...I mean don't be mixing oils all the time but as long as it's drained properly there should be zero problems

and even if it isn't drained properly, there really isn't any harm in it happening once like this

 

well this is the third time that this has happened at this dealer. So I really don't know how many miles it has on it using regular oil verses syn. But an estimate would be 12K on reg and the rest of the 52500 on synthetic. Just concerned about a warrenty issue

 

Regular oil changes at the factory intervals with the right weight is ALL that is required to maintain your warranty, as far as engine oil changes are concerned.

Synthetic/conventional is not a variable in that respect.

 

What Mike said regarding warranty ^^. If you check your owner's manual, the only requirement is for an API-certified 5W30 oil.

There are no issues associated with switching between different types of oil or from regular to synthetic between changes. In addition, the only real danger of mixing the two at the same time is that you might lose any of the potential benefits (assuming there are any) you would get from synthetic oil instead of regular.