Are there any products that do not produce outgassing that could contaminate optical components? (Would No.0 and No.2 have less outgassing?)

The principle of the temperature at which grease volatilizes is 198°C, which is basically the same for all manufacturers' greases.
The temperature at which the thickening agent (sponge) of grease becomes liquid (optimum point) is around 100℃ for more than 80% of general greases, but for Bellhammer, the temperature is 199℃ or higher, making it a type that is difficult to outgas.