First of all, I really enjoy this forum. There are several very informative people here! I try to exhaust all search possibilities before posting a topic. I think this one is new?!?! I have a '01 PT Cruiser, run M1 10W-30 Synthetic and want to take full advantage of the oils potential within the manufactuers recommendations. What is the MFR extended drain interval for this engine? Secondly, other than 5W-30, what other viscosity can I run in this engine?