Go here:
http://www.bobistheoilguy.com/You will be able to learn everything fit to argue about oil and oil additives.
Had an older guy, older than me anyway, come up to me while I was idling my truck waiting for the wife at the grocery, he said my engine sounded rough. "Thanks,for telling me I said, but it's a diesel engine."
I use Amsoil Series 3000 Heavy Duty Diesel Engine Oil in my trucks, along with a dual bypass filter system, oil analysis and very extended change intervals. I wouldn't put any additives in these engines, the oil works just fine as it is, but at $12.10 a quart retail it should.
Anyone who uses oil of the proper specification for the vehicle and maintains it according to OEM schedule shouldn't need an additive. I found the various full synthetic oils to work best if the drain interval is extended out beyond the recommendation, backed by used oil analysis, otherwise the added expense isn't justified. The use of a bypass filter system protects the oil, not the engine, and is also only practical if one changes oil no more frequently than 25 - 30k miles, or more.
Slick 50? I don't think so.
