I was reading through the maintenance manual for my 525's and saw the oil change frequency should be 25 hrs or 30 days!!! It's hard to believe that the oil will degrade by sitting in there for 30 days. Is this just a way for Merc to get out of warranty claims?

30 days?!?!? Maybe to get the water out from the leaking CMIs?

Seems excessive. Hook up with a local oil analyzer company. Run you oil for 1 month and send a sample, then run 2 months and send another sample and view the results.

Amazing the info that will give you. Here local it is only $12, $3 more for filter and they save your history and give you a comparison print out with layman and techy terms.

With synthetic oil 50 hours should be no problem at all. When you do start the engines just run them enough to get the oil temp high enough to burn off any condensation in the oil.

If you dont run 50 hours a season just change it once a season

I just checked my manual and it does in fact say 25 hours or 30 days whichever comes first.

The 25 hrs. sounds resonable, but the 30 days sounds nuts. This yr. I doubt I will do much more than 10 hrs. /month. I'll change the oil half way through the season and it will be fine.