Engine oil choice

[Journey!]

My 1993 Crusader 454’s owner’s engine manual recommends a straight weight 40W oil. I use Rotella. Anyone else?

[bud37]

Welcome to the forum.....how many hours on your engines ?

[km1125]

Using a multi-viscosity isn't going to matter. It won't get cold enough while you're using the boat for the "W" rating to be effective, nor necessary.

[mjk1040]

Rotella 40W is all I ever used in our Crusaders!

[waybomb]

I run Rotella but also add a can of the old GM EOC. It's very high in zddp.
I wiped the cams in the Cougar years ago when they started changing oil so it would not clog catalytic converters. They removed the zinc. I was running flat solid lifters. Wiped all the engines' cams. I bought a bunch of the original EOS and have a lot left over, so I use it in these old Crusaders.