I figure before the wisconsin winter decides to make working outside unbearable, I'd do a oil change quick.
I bought two manuals off of ebay, but none of them seem to spec out a specific type of oil....

From wondering through the interwebs and forum posts, I've heard that these older diesel engines require high sulfated ash content. These meet the JASO DH1 or GLOBAL DHD1 standard? The newer oils seem to not have contents over 1.0%. I might be looking into this too deeply....
I've also seen a wide variety of different weights on posts. 10W-40, 15w-40, 5w-40?
Any information would be fantastic. What have you been using? How much? Techniques for oil changes?
Thanks again!