Under most circumstances, lubricant is properly used very sparingly or not at all. In nearly all SCUBA applications, if you can see the lubricant then you have used too much. Lubricant is often improperly used excessively, and prior to use any existing lubrication should be completely removed before reapplying new lubricant. Lubricant is NOT a "sealant" and is not used to create a seal. Most lubricant is used with dynamic seals in regulators to reduce excessive wear. Lubricant is also used in rebreathers to ease assembly of loop components that incorporate very tight connections. As a general rule, the O-rings used with static seals in SCUBA applications should not be lubricated at all. The lubricant just causes contamination to stick to the surface of the O-ring and results in more problems with a static seal than any dubious benefit the lubricant might provide. Dive Gear Express does not recommend the use of any lubricant when installing SCUBA valves in cylinders for Nitrox applications.