I purchased some of the older conventional Valvoline 15w-40 diesel oil for break-in. But even diesel oil has been getting the zinc taken out of it bit by bit. It's been difficult to keep up-to-date with the latest formulations unless someone send it out for testing. But afterwards, I use one of Amsoil's thinner thinner oils. They have several that specifically say they have high zinc content, particularly for flat tappet cams, including a new line of "Dominator" racing oils.