As you all know a while back my temp light would come on about once a day and go off after about five minutes of cooling. Checked hydraulic fluid and it was full and clean. Actually it was too full which is how it was when I bought it. I asked several people if it was a big deal and no one acted like it was so I left it. Well I decided to drain some after looking in the manual and read that it should not be overfilled due to expansion. Took the plug out and the fluid looked very black. Decided to go ahead and change it and the filter. Machine acts fine now but I have not done any heavy digging. It seems like its allot quiter. I noticed some people use hydraulic oil for the hydraulics and some use engine oil. Which do you prefer and why? I used 15W-40 since it referred to Super- 50.