I run the Pennzoil 5-30 with Marvel Mystery Oil since I bought the car used in 2004. I have had nothing but better and better performance since then. I use marvel in my fuel as well.
I also change my oil and filiter at or around 3k miles. I put a quart of the marvel in my oil instead of one of the quarts of regular oil. I add 4oz of the marvel mystery oil to every full tak of fuel. I usually drain the tank to just above "E" all the time so it works well.
My father always used it and it works. Hell he got 480k miles out of a mercury sable wagons engine. All he ever used in it was regular oil and gas w/ the Marvel Mystery Oil in both.
I know this sounds like a rant on how good it is, but I use it will almost no problems at all. I even get almost 300+ miles on a single tank of gas city driving that is.
