Flat tappet=high zinc (over 1100 ppm), 10w-40 if you operate in colder weather, hotter weather 20w-50. 15w-40 and 25w-40 are okay also, not sure I would would want a 10W-30, if you get any fuel dilution, it goes thin real fast. Redline, Amsoil, Joe Gibbs have high zinc oil, look through the vigin oil reports and see which oil have the high zinc (high moly would be good too) and choice one of those. Most off the shelf (Walmart, Auto Zone etc) don't carry high zinc oils, they carry SAE oils which have reduced levels safe for catalytic converter and now low calcium safe for DI/turbo engines too. I'm not sure about the levels in HDEO oils.