I think i did not make my self clear i am not talking about mixing oils, and not messing up with viscosity, almost every mechanics says if you are using Havoline dont go for Zic or Helix engine may emit smoke? I could not understand it and thats what specifically asked if anybody could tell me.
I changed three brands for my car over two three years' time period but nothing happened.
But faiz i really enjoyed your comment about mixing sprite with tea and will give it a try.