Break in oil for break in, and a ZDDP flat tappet type oil for after break in. I've seen this scenario a number of times. Customer breaks in motor with break in oil. Then switches to ZDDP flat tappet oil. Then cheaps out and changes to what ever Wally Marts got on the shelf, and then the cam loses some lobes. Dozen + times over the years.
Not all synthetic oils are good for flat tappet motors either. Just like their conventional counter parts, some have a good ZDDP additive pkg some don't.
The diesel oils still have a fare ZDDP content, but they have a high detergent level which counteracts the ZDDP benefit to some extent.
I don't get why people still cheap out on something like an oil change. The extra $2 a qrt for a good ZDDP type oil like Valvoline VR1 is going to add a whopping 10 bucks to an average oil change. In the grand scheme of things car related its a drop in the bucket.
