I have a 2008 Optimax 200XL outboard and used Merc's oil for a few years, then switched to an Amsoil product (both without any problems) but I've heard Pennzoil's XLF is another good and somewhat cheaper alternative ($17/gal via Amazon Prime). There are a few threads on The Hull Truth and a some other forums discussing this, but I figured I'd ask this crowd.

What DFI oil are you running in your Opti's?