My parents gave my daughter their old 2002 Trailblazer a few years ago when she went off to college. It had maybe 145K miles on it when they gave it to her. They had always used conventional oil, so I stuck with it. A few weeks ago she was home and I did an oil change. I didn't have any conventional on hand so I used some syn blend Castrol Magnatec 5W30 that I'd bought a while back. I was under her car a few days ago (starter went out--grrrrr!) and noticed a little bit of oil. Nothing was dripping yet, but there was a little oil noticeable. I'm wondering if going to a syn blend started an oil leak. :-( I hope not because no matter how often I tell her to check her oil level, she never does. Do leaks that result from changing oil brands/types ever clear up or is this just something that I'm going to have to deal with? I doubt it is anything I'll fix...I'll just have to monitor it.