When you're comparing the 2-post and 4-post, they pretty much work exactly the same. Both lifts are going to have an electric over hydraulic pump system, meaning you have an electric motor that's connected to an oil pump. That's into this valve block that has a suction tube going in the oil tank. So when the motor runs, basically you're pumping oil out of this tank through a series of hoses - one going to the cylinder on this side, the other one going overhead to the other side. 

This is a two-cylinder two-post, which is fairly common. Many years ago, I've run into one-cylinder hydraulics where they were chain drive, but this is a two-cylinder hydraulic system. Now our pump - you look at the size of these cylinders and you wonder how that little cylinder picks up so much weight. Well, this pump pumps 3,000 PSI and you got two cylinders - that's how you get your 10,000 pounds of lifting pressure. 

As far as maintenance to the system, there really isn't a whole lot to do. Once you have this system in and bled (which in this instance, the chain over cylinders are self-bleeding), it's pretty much there for the extent. What you will notice and may have to have repaired down the road - and that should be far down the road - is sometimes a hydraulic hose will start to leak, but you'll see it dripping on the floor. So you just see where it's coming from and replace that hose. You have a short hose there, you have a short hose going down here, and you have a long hose going up overhead. 

The other place is your cylinders. Of course, the rubber seals run inside a polished bore. They can leak, and if they leak, you're just going to see oil. There's a vent at the top of the cylinder - oil will start to run out that vent and down on the floor. Again, that's a possible rebuild or replacement. 

Some people want to replace their hydraulic oil in here after so long. It's not recommended - you can if you want, if it makes you feel better, but pretty much the oil doesn't get hot. It's not like an engine where it makes your oil hot and it can break down. This goes up, it takes about 60 seconds to run up - it's not going to heat up that oil. 

One other thing that's unique, and this is for the Backyard Buddy (the Advantage doesn't have it), is it has a vent tube. If I were to get you back there - this cylinder is a single-acting cylinder, so it has a vent at the end for air in and out. Well, if oil were ever to get by that cylinder, even a small amount, by design it's going to drip onto your car. So even though it's only a drop or two of oil, you don't want it on your car. So with this one, we return that oil back into the tank so you never know it's even dripping. 

But what this has that the 2-post doesn't have is this secondary lock system. Because by design, these cables on this lift, unlike the two posts that are actually picking up the vehicle, your hydraulic cylinder is underneath the runway that pulls all four cables through a series of pulleys. So now your cables are actually picking up each corner of the lift. So what you have to have now - if this cable were to break, what's designed in the lift is what we call a secondary lock. When that cable has tension on it, it's holding a lock independent from the one you control that it's setting on now. So if that cable were to give slack - hear that click - that's that lock engaging into one of those windows for safety.