I guess I misread the initial question and answered relative to the engine oil dipstick. My L2501 has a sight glass on the left side just below the clutch. There's a half circle cutout on the metal where you can see the window. When I changed my filters I had to add about a half gallon of fluid to bring it to the halfway mark on the window. I did not check it before changing the filters. Note - I have added John Deere hydraulic fluid dye to the system to facilitate viewing fluid level. Disclaimer - Kubota will not be responsible for any damage caused by the addition of the dye. The mechanic at my local dealer said he checked with Kubota and the dye will cause no harm. It that point I got brave and used the dye.