- Sep 28, 2005
I've always used Castrol GTX 20/50. I just came back from the store with some and noticed that the new ones say "anti-sludge formula". Is this something new? The old stuff was rated SL and the new stuff is rated SM. Busting sludge loose doesn't sound like such a good idea. I hate to ask, but what are you guys using if the new Castrol is a problem?