I've never had hydro problems on any mower I've ever had. I've always changed hydro fluid (30 weight motor oil) and filters around 350-400 hours. When I change, I put a little peice of duct tape on the filter and write the hours on the tape with a Sharpie pen. I do that for oil filters too. That way I can see when it's time to change again at a quick glance. If the duct tape doesn't stick, I've also used a paint pen from the hobby shop and that worked well also. I couldn't really tell you if the filter is different from a car filter. I've always gone with the recommended filter and never gave another thought to it. As far as aftermarket belts and such, I've always used what the dealer had and never had any problems. He does sell aftermarket to save a little money. They work fine for me. One thing that I've never been very happy with are the tires that are available in this industry. The have no real life span to them. As they wear a little they start bulging in the middle of the tread causing an uneven wear pattern that looks like the tire has been run overinflated for a long time. It's not from too much air pressure, but rather, from the tread wearing thinner. On the fronts I have them foam filled and the backs I run "slime." I also carry a plug kit. They get to a point where you can run over a rose bush and poke 'em full of holes. However, if I foam fill the fronts, they will last for years and years and years. But I can't fill the backs with foam because #1. they'll be too heavy and #2. they'll be way too rough riding. If you want to foam fill the fronts, look for a company that services fork lifts. If they don't do it, they'll probably be able to tell you who does.