As long as it meets the mfg'rs specs, any oil will do. Merc probably does not have an oil refinery, so someone else makes their oil for 'em to their specs. I have an 04 Merc 60 2smoke, and have used quicksilver since new until late last year when I bought some Pennzoil.
I'll share this for what it's worth. I took an outboard engine repair course back in the late 70s taught by a BIA certified instructor. I had a nearly new 4.5 HP Mercury engine.It ran like a top but was hard to start first time each trip. Had to pul and pull to get it started. After that it started with one quick pull all day.
I took it to the class and we checked everything from top to bottom and it was up to specs. Instructor asked me what kind or oil I used and I told him I bought it at gas stations, probably Penn or similar brand. He told me to switch over to QuickSilver oil which I did. After I had run all the old gas out it started cranking on the first pull every time, hot or cold.
Made a believer out of me and I have run Quick Silver ever since, even in the Johnson 35 HP that I ran for 20 years.
Does it make any difference today?? Can't say, but I just buy the gallon of QuickSilver and it last me a long time. I don't have a big outboard so I don't use a lot so the cost is not too big a deal.
Quicksilver is good oil.....been around a long time......I don't think it is good to switch oil on any engine.....
Thanks to all, just went ahead and bought me more of the Quicksilver, ifn it aint broke, don't worry bout fixin it :)