i’m going to begin fluid changes. Spoke with PO who said it had been a few years. Have a service manual now,?but my research is showing about as many different engine oils being used now as old jeep owners, ha...diesel oil, zinc additive controversies, flat tappet stuff, etc. anyway, I need engine oil and replacement oil filter. Trying to stay original, and recommendation help appreciated. Will proceed with tens, transfer case and difs next, thanks.