What lubricants are safe for a spring gun and which should I avoid?

Use silicone chamber oil (high flashpoint) on the piston seal and breech seal, applied a drop or two every 1,000 shots or when the seal squeaks on cocking.

Use a thin film of moly or lithium grease on the spring; avoid heavy tar greases that trap dust and feed dieseling. Never use petroleum-based oils (WD-40, 3-in-1, motor oil) inside the compression chamber of a modern springer with synthetic seals: they cause dieseling, swell or rot synthetic seals, and can detonate. RWS Chamber Lube and Pellgunoil are common safe choices.