Some of you may have seen my previous post about changing the hydro oil in my 757 at 390 hours. Well, I did the change today and am glad I did. This is a PSA to check your fluids. The previous owner I bought this from was meticulous with maintenance, but it looks like he may not have been changing the hydro oil enough. Attached are some photos from the change. The substance on my finger appears to be from water that got in the system and created a foamy grease-like mixture. There wasn't a ton of it, but I'm glad I did the change. Taken out was 2 gallons of (likely) factory fill and put in was two gallons of Mobil Delvac Extreme 15W40.