I'm of the opinion that diesel oils blacken so quickly that I change them quicker than the recommended intervals and so synthetic oils are a waste. I do use synthetic hydrostatic fluid though. In that case I believe it is warranted. Just MHO.
In all of our tractors we run 15w40 all year round.
I change oil every 100 hrs.
A synthetic is a thinner oil so if you believe the cost is justified go with the synthetic 15w40.
But wouldn't a block heater be less expensive?
Also remember once you switch to synthetics you should stay with them.
I use 15-40 diesel blend in everything, my 2210, 4520, my 1955 jd70 Diesel, the 6300 and my cummins truck.. I use it all year round. Either they are plugged in or in a heated shop. I'm north of Billings Montana by 9 to 10 hours.
Come to think of it you can get a rear end heater for your unit.. I picked one up for my 4520.. I should get that installed.. winter is coming soon.. :crybaby: