Hello. I would like to know what's the best dino oil that fights sludge and keeps engine nice and clean, while doing good job in lubricating. I heared some stories that engine were torn apart that were using Castrol GTX and had lots of sludge. Someone probably heared something else. So, what's the bisuness with sludge and carbon deposits and oils??? Auto-rx suppose to clean out and synthetic oil are better keeping engines clean, that's all I know. But on my car I use dino. It's an Subaru 2.5l engine.