I'm new to a Yanmar tractor but been around diesels for a while. I've had very good luck with Rotella oil 15w40. It's a good all around oil for summer and winter both. It's also easy to find from Walmart to any auto parts store. As far as Hydro, rearend ect. I get mine from NAPA. It's called universal tractor fluid. If you read the back of the jug it will tell you what it is compatable with and I think it will serve you well. Hope this helps...Southpaw