Been running the Mercruiser oil since new but since it's now out of warrenty is there any advantage or misgivings about switching to a sythetic like Mobil1 when the engine has this many hours on it with dino oil?

I bought my 496HOs with around 1 season on them. Previous was all Mercuiser oil and filters.

I immediately switched to Mobil1 15w50 with a quart of Lucas Oil Treatment; with only Napa Wix Racing Filters, 1060R filters.

No issues whatsoever with anything internal, and I occaisionally cut open my filters with no indications of issues; now over 250 hours.

went to mobil 1 at about 30 hours on the second change, also with Wix/Napa filters. No issues. I'm at 200+ hours and niether goes down a drop between changes regardless of operating conditions. I change it now at 30-40 hours. I feel good about synthetic in my engines.

45 hours on my HO's.....may try synthetic at next oil change...will go with what my dealer/ service shop suggests.

11 engines over the years with Valvoline Racing 40 weight. Never had any issues even up to 850 HP Blown. Longevity as far as bearings cam and wear points---- Excellent. I'll stick with what works for me, I don't want extended time between my oil changes, I like to keep an eye on what's going on inside.

From some reading I have done on synthetic, the water seperates on the bottom rather than on top with reg oil, which burns off easierfor reg oil...all motors contain moisture...

If that's the case, that's more than enough reason to stay with a petroleum based rather than a synthetic especially in the marine environment which creates more moisture in any and all systems. Water can't evaporate off the bottom of a pan very easily.

I've seen people change to synthetic in as little as 20 hours with absolutely no long-term problems. I always wait untill 50 hours or so myself.

In order for this to be a distinct disadvantage of synthetic, the pickup would have to be scavenging right off the bottom of the pan, literally sucking right off the metal of the pan. Marine engine or not, in a 9-10 qt. system, moisture as related to volume is nil (unless you have issues, see below). So what do you think? moisture boils off the "top" (of dino oil) of the volume in the sump like mom's pudding (skin) ?? If the (dino) oil sitting in the sump is that hot or boiling...you've got bigger "issues".

Nooooo. moisture is evaporated back into atmosphere when it is heated and squeezed at the molecular level on mating and wear surfaces! So it's all the same...in respect to oil (in use at operating temp) ridding itself of H20.

If your accumulating enough moisture to make this even worth discussing you have cooler leaks, reversion issues, or are running your engines too cold an operating temp!

This whole bit about moisture is a moot point. Don't get people worrying about something that is NOT a factor in the choice of dino vs. syn.

So switching with 190hours on the 496 won't cause gasket issues ????

Don't need no stinkin oil leaks and I've been told by a auto mechanic that my motor has too many hours on to switch over now... So no-one has ever seen leaks after switching over ????