BCB is correct here. The hydraulic steering system does not “use” (consume) hydraulic fluid. That being said, removing that cap and looking inside every 3 months is a good idea. The level will fluctuate a little depending on temp. Fuller in the hot summer, a little lower in the cold winter. The reason for looking is to get a sense of the normal level for that time of year.
If it starts to drop, the fluid is going somewhere. If you are mechanically inclined, you can search for the leak. There are only two normal points of leakage, one obvious, one not-so-obvious (unfortunately MUCH more common).
A leak at the helm will leave fluid on the carpet which makes it pretty easy to spot. If your socks get oily while driving, look here first. 🙂
A leak back at the cylinder is not as obvious. The oil will drip down from the cylinder and get hidden by the water at the back that can wash it away.
On either end, first thing to look at would be the line connectors. Just rub your fingers along them. Should not be oily/messy at all. If the leak is at the helm, and not at the connections, this becomes harder to fix. At the rear, there are seals around that shiny pushrod you see. Those tend to leak on a SeaStar after a few years.
Best bet is to always just take it to a dealer and let ’em luck. Steering is one system you can not afford to play around with and get it wrong. At 70mph+ that can be a fatal mistake.
That being said, the “check” is important. It will let you know you have a problem before it becomes a BIG problem. Just don’t pour hydraulic fluid in and assume all is OK. It probably isn’t.
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