Spruced up the tractor and our “new” PZ Zweegers HayBob. one full tube of Syntec Grease, 5 liters of Rotela T5 semi-synthetic 10w-30 and new fuel and oil filters. Still dirty, but it runs like a new tractor. Begone, normal 5w-30!! Thou art bannished!! The semi-synthetic has a low enough pour point that I can run 10w-30 all year, and it likes it. Smoooooooth, almost zero valve noise now (and this is a diesel, remember!)... also, 5 liters of oil for a 1.6l, 30hp OHV engine? Yeah, thats probably overkill, just like a tractor should be.