Diesel Engine Oil Change Frequency?

[Kenomac]

I know this has been discussed before, but I'd like to put a new angle on it. Here I am hunting down the appropriate oil for my Yanmar 100hp turbo diesel and Westerbeke 10kw generator at the end of the season.... and wondering if it's even necessary to change it? Here in the Adriatic for six months, we covered about 1200 NM, but having installed a 450w solar array and basically sailing most places on new sails, we've hardly used the engines.

Only 100 very easy hours on the main engine and maybe 60 hours total on the generator. Do I even need to change the oil this season, or can I let it go for another year? Seems like a waste of good oil, neither engine burns any. We didn't even go through a full tank of diesel (less than 225 gallons).

What do you think? Geez... I just realized I haven't changed the oil in my diesel Bobcat for eight years... and it gets more hours than my generator, and runs perfectly all winter long... in below freezing temps.

And if I do decide to change the oil, is this stuff OK for the Westerbeke generator? Nowadays, most oils on the market here in Italy seem to be formulated for all engines diesels included, and most are synthetic.