Hummmm ... I sure thought what Dennis posted was what I posted several replies earlier without the photos of oil bottles.
As for the explanation ... some owners of RV's with the level up system installed experience popping noises after they set up on the campsite. For no better description, it is settling of the RV on the hydraulic jacks. Thus the popping noise. Lippert has suggested adding an oil additive in place of some of the oil already in your hydraulic reservoir to cure the issue. We are not talking about a leak, but popping noises as the RV settles in. If you don't hear any popping noises after being set up ... no need to go out and buy the fluid.