Hi wise folks, I have a 1840 Case skid steer I purchased new in 1989, great machine. I am fanatical about service and usually change oil and filters etc well before the suggested hrs. It has used( as specified in the manual) Case #1 10w-30 engine oil + 2 quarts HTO additive for hydraualics and hydro static drive since new. I am about to do a change again and happen to have quite a few pails of heavy duty full synthetic CK-4 diesel oil 0w-40. Would that be a better choice? I know most would say stick to what the manual recommends, but that was written in 1989 and maybe full synthetic would be a better choice now. Thanks