Around here, there is a prevailing myth,or so it seems, that Castrol GTX is the best for a smaller engine. I've heard several folks say "If I had a 4 cylinder, I wouldn't run anything but Castrol." What is your take on this?? I wonder how this may have gotten started? I must say I bought into it,because I use it in my two lawnmowers. My wife's parents bought her a '90 Sunbird with low miles back in '91. When she got her GTP, I took it over as my daily driver. We have put 140,000 miles on it using Q/S 5w30. It still runs like a top. We even used Fram filters for years before we heard how bad they are. So how about this "myth?"