I had a 383 professionally built and dynoed for my 65 Impala. The builder is telling me to use Lucas 20/50 Break in Oil all the time because it has the highest zinc content. Using "break in oil" all the time sounds wrong to me. People are also telling me that is too heavy of an oil to use. He did say if I was going to drive the car in the real cold months to use Lucas Hot Rod/Classic 10/40 high zinc. I just want to use what is right for the engine