Don't know about the larger engines but I used Pennzoil in my 1995 75 HP engine till this summer (the whole 15 years) when I sold it. I never changed the plugs or winterized it ever. It never failed to start one time. It turned over and started the first crank this spring...it was cold natured though but ran like a top. I would like to think that all Mercury motors would perform like that but...reading this forum makes you think they're ready to blow up any minute and 10 hours on a motor is an ancient Merc .

My new 200 though, I'm kinda stuck with using the DFI oil in it. I wonder if it really makes that much of a difference? I don't know but it's a lot of money to me to not use the DFI oil and take the chance