I know this subject has been beat to death, but there does not seem to be a definitive answer. Bobcat suggests 10w30/10w40 motor oil "in an emergency" . That tells me it is not the ideal oil to use. I was also told by a Bobcat technician, that the "Bobcat Oil" is supplied by the lowest bidder, and the brand will vary from lot to lot. Additionally, he/others said do not use "tractor oil" if memory serves me correct. As I may have mentioned in another post, I talked to a local oil dealer who recomended using Mobil DTE15M. Now, I am faced with the additional problem of a machine in good condition, but needs the filter changed. Of course I will lose some oil in the process and I have absolutely no idea what kind of oil is already in it. I cannot believe that mixing motor oil and hyd. oil is a good idea. I realize both are oil, but that doesn't do it for me, as I have had the $$$$experience on hydrostatic pumps/motors several times and am painfully aware of just how important the proper oil is. No, personally I don't buy the "cheapest" as you get what you pay for. So, what's the best solution? Really depending on you guys. Thanks, John