Re: 20 hours on diesel this summer. change oil or not?
I've got the almost identical situation Jason: 4108, very low hours this season. My boat gets pulled and winterized for the winter months and I always change the oil at the end of the season, no matter how many hours I've put on.
I'm far from an expert, but I've always been warned that used oil will contain acids that are not good to sit in your engine. Changing oil seems to be a cheap and easy way to help keep the old beast working well. I have skipped changing my filter some years, but always change the oil.
Why go fast, when you can go slow.