Forum members, my Unique has a 351 Cleveland. The engine has about 19k miles on it since it was rebuilt. The previous owner used Rotella T synthetic exclusively and cited a need for high zinc content for the flat tappet design. Apparently this oil is designed for heavy duty engines (i.e. truck). I have heard the need for high amounts of zinc in the oil for break-in for flat tappets and not necessary after that. I have also heard that running synthetic in a "vintage" engine (circa 1971) may promote leaks as opposed to a non-syntetic oil. I want to put the "right" oil in this engine to keep it running properly and would appreciate any feedback on what is "right" for a Cleveland 351 engine. Thanks, Chris