I have some various equipment (tractor, generator, etc.) that have flat tappet cams and I am wondering if the newer API-rated CK-4 diesel oils will provide enough protection for engines that are already broken in? I'm sure the spring pressures are not substantial on these stock one-cyl or 2-cyl motors but I know there is less anti-wear additives in the newer oils and wondered if I'd be better off sticking to some older rated motor oil such as SL or SJ which can still be found.
