Just bought this to replace the aging and now weld-cracking jack i had. In the owners manual, it says to drain all the hydraulic fluid every 6 months and refill. I will used it once every 5k miles so about once every 5 months. I believe it spec'd WD-40?? Any good fluid you'd recommend? Btw, i never changed or drained any fluid on my other jack. Only added a little before each use.