I'm done a search and found a few post regarding my question, however the posts I found were for the 1st gen blazers.

I have an 05 jimmy with 96000kms and I am doing my first oil change on it. I'm not sure what type of oil (dino/syn) is in there already.

I bought some Pennzoil Platinum from walmart on sale, which have "cleaning agent" additives. I was wondering if I can use this safely and not have any leaks. Im worried that the "cleaning agents" would make the seals/gasket soft and make the oil seap out.

 

There is the possibility of the synth oil softening some seals causing them to allow some temporary leaking, but as they become a little pliable, the leaking should stop. Then again, there may be no leakage at all.

 

My 99 BlaZeR2 has 127,000 miles on it. Since buying it with 80,000 miles on it 3 years ago,I have been using high mileage non synthetic oil in it. I did try the Valvoline Max high mileage that is a synthetic blend and i had a few leaks so i just kept using the Wal Mart high mileage oil and to date have had no issues.