Hi Ally, long tome no see but i am still around hehehehe..aboutt he knees you must first go to a store that sells hydrolic stuff and they should be able to help big time. They can no doubt tell what kind of fluid is it in to. Bring one of ur knees espically if one of them is leaking, they can look at the fluid and no doubt determine what kind it is. Dont forget to adk how much fluid is in any type od cylinder and ask if its proper to fill it completely. You might not have to do so..Heck they might even help you out in refilling it.