Very light use of silicone is fine for O rings, provided it is a sufficiently light coating that it cannot migrate to any high pressure threaded connection. It is not a lubricant for high pressure connections, and can cause seizing of the parts. Upon the recommendation of a high-end air gun maker, I use synthetic Mobil 1 oil and grease for lubrication on, or close to high pressure connections. A quart of each will last a lifetime.