I got '05 Envoy SLT and had a small oil leak (may be two drops a night). Checked the engine and I can see the oil at the back of the engine looking from passenger side under the hood. So after seen more drops I took it to dealership, they put the die in the engine oil and told me to bring it back after two week to check leak. They found oil was leaking from around the head gasket and at the exhust meet the head area. It took them almost 5 days to fix the problem since lots of the parts they had to order it. Just writing to make sure nobody else has the same problem. They replaced headgasket plus all other gasket in between. Warranty charge (since truck was GM certified used " Thank god ") for the dealer was more than 1200 dollars. The sales guy was saying something like this can cost the consumer around 1800 dollar at the dealership. It is been a week and I have not seen the leak yet. Hope this one does not happen again.