I just use the regular oil treatment. I contacted STP when the zinc went from the Delo and Rotella. Their rep said one bottle has enough zinc to treat 4-5 quarts. There is a new additive out now that is called ZINC but on the back label it says there is no zinc in it. How does that work? The only sort of regular, off the shelf, oil that still has zinc is Valvoline Racing Oil. Tom

"I wonder if God created man because he was disappointed in the monkey?" Mark Twain