Oh lets talk oil... again.
First, congratulations on your tractor! I love mine! It's a 2018, well, thats when I bought it new.
Contrary to what others may think, you wont harm anything by changing the engine oil twice or three times per year. The only thing that will get hurt is your bank account. Conversely, you can do annual oil changes. I wouldn't go over a year though. When oil starts to break down, and then sits, it seems to oxidize or get sludgy. Bad things happen. But once a year should be good.
But lets talk about the advice you will receive asking such questions on this forum.
Consider your tractor. And please look at the tractors of those who give advice. I'm not naysaying their advice, but sometimes people will post advice about your tractor, thinking its the same as theirs, when it's not. For example, our tractor has a small little turbo. That turbo is extremely finicky about the oil. Do a quick search on this forum to find several posts about turbos blowing up on these tractors. And the most common reason they fail is due to lack of maintenance, not letting it cool down properly, or using the wrong oil.
So what type of oil for your tractor and your climate?
Any 5w-30, 0w-30, 0w-40, 5w-40 will work just fine. If you wanted to do a winter and summer oil change, I'd go 5w-40 in the winter and 10w-30 in the summer. I also run full synthetic, and tend to grab the bottle thats says "for diesel engines" but not always. I have run standard Mobile 1 in my tractor (which is what's in it now) with no issues (knock on wood.) The Shell Rotella T6 mentioned here is great. That will probably run just fine. It also depends on your actual climate and when you're using the tractor the most. Does the tractor get used when its -20? Is it stored outside without a block heater, or in a nice warm shop? The summers months, are you out working your tractor HARD when its 104? Take the average, run that oil.
A quick note about the owners manual.
They are a great resource for a starting point when it comes to basic vehicle maintenance. This goes for any vehicle owners manual. I will always state "to follow the advice in your owners manual and ask
your dealer for clarification." You don't have a dealer, but I'd go ask him/her anyway. They might be doing a repair on your tractor in years to come. The reason I state this is because of liability. The same reason that goofy chart is in the owners manual. Its CYA. They cannot list every weight and brand of oil in the manual, but they will list the extremes. And when something fails on an owners tractor, they can point to the manual and show the wrong oil was used. Manual on one side, practical experience on the other. Don't over think it. Just change the oil at least yearly.
Hope this info helps! This forum is an amazing resource! Feel free to ask questions and post regularly. We also love photos!