AS told to me….There is only a couple of outfits that make boat oil. It is all contracted. I think BellRay used to make a lot of it. Maybe someone else has the corner on it now.
The difference is the additives. Don’t ask me what they all are.
The motor companies blend the oil the way they see fit for their engines.
TC-W3 is just a rating. The motor companies exceed that rating. Off brands and house brands meet the rating. It is just a rating. There is no higher than TC-W3. There used to be TC-W2 but notice it no longer around. All engine manufactors now require TC-W3.
I don’t know what the bloody heck TC-W3 means.
But I ran Quicksilver Premium Plus in my 200 EFI. I’m not taking chances.