I'm on my second year with the IS1500Z, last year it really just served as a backup and cut my own yard but this year my accounts are such that it's being used pretty heavily. This is my first hydro unit and as such I'm not super used to the idiosyncracies of those drive units. What concerns me is that at 25 hours I did my check on the hydro resevoir and noticed I was down a tiny bit. I double-checked the units, the connectors and watched for drips or leaks. Had none. At 48 hours, I'm down even more (I'd guess 1/5 quart). I topped it off, still no leaks or issues, but I'm wondering if this is a normal attrition of the units but I am thinking with a closed system like that they shouldn't be losing any at all. Is my experience normal, I'd like to know as I'm still going on some warranty and want a more "real world" answer before talking to a dealer that will no doubt assure me that anything other than a 250 degree engine fire is "how they all are". TIA.