Hydrostatic Transmission Fuel Cold Line - Hard to Read

[JD_Driver]

I've had my mower for 3 years (Snapper Pro S200XT - bought it used at 400, now has 580 hours on it). It went in for repair and I had them change the hydraulic fluid as well. In the last 3 years, I never changed or added the hydraulic fluid, I had heard that it's good for about 400 hours (please correct me if I'm wrong).

But after a hydraulic fluid change and mowing for 6 hours, I noticed the right expansion tank has tiny bit in there, but the left expansion tank doesn't seem to have any or barely a little. The cold line is also a bit hard to read, but there's an indentation on the rear facing side of the expansion tank and I'm wondering if that's also the cold line

I'll also mention that before I saw the hydraulic fluid levels - my drive belt had come off, I had lifted the back up for about half a day to remove the drive belt and put on the new one and then I mowed for 1 hour and that's when I checked the hydraulic fluids.

So my questions were?
1. Could the hydraulic fluid be less because it was just changed and maybe the mower used it up a little?
2. Is the indentation is where the cold line should be?
3. Should I use 20W50 Oil for it?
4. Why is the cold line so far below - does it ever expand a lot when it gets hot?
4. Off Topic - what kind of life can I expect out of this Commercial mower - Snapper Pro S200XT?

Thank you

It is often also helpful with things like this to try a different method. What seems to work well is to remove the fill cap take a flashlight and shine into the opening. The fluid level will show up darker on the outside of the reservoir tank.

 

[Tiger Small Engine]

It is often also helpful with things like this to try a different method. What seems to work well is to remove the fill cap take a flashlight and shine into the opening. The fluid level will show up darker on the outside of the reservoir tank.

20W-50 synthetic oil for hydraulic pumps and drives. Simply keep an eye on oil level and top off in expansion tank reservoir as needed. Not uncommon for pumps to have small leaks over time.
Snapper has never been a player in zero turn or riding mower market. Rarely see them in my shop (first zero turn ever this year). Life expectancy should be comparable to other zero turns and depends a lot of maintenance and use patterns.