Hope this is not a stupid question but I have heard a lot people say to drive with the engine brake on. Why is that? I have tried to find posts on this subject but have not been able to find anything (I am sure I just missed them). I was also thinking of running Amsoil in the engine. Is it really worth it? Any insight would be greatly appreciated. Thanks

P.S. I have a 2009 2500 which I have had for just a few months.