Maintenance · How-To
CO2 airgun care: seals, oil and storage
Researched by James · Updated September 26, 2026 · Editorial policy
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This routine reflects standard guidance from airgun retailers and manufacturers linked in Sources. My own rifle is a regulated PCP, not a CO2 gun, so the seal-care habits below come from that published guidance rather than my own field routine. Full methodology & editorial policy →
Why CO2 is harder on seals than PCP air
A PCP fill pushes room-temperature compressed air past the fill probe's o-ring once per fill, and that's the extent of what the seal deals with. A CO2 cartridge is different: piercing it releases liquid CO2 that flashes to gas and drops in temperature as it expands, and that cold, high-pressure moment happens at the piercing seal every single time you install a fresh cartridge. Do that enough times without any lubrication and the seal dries out, stiffens, and eventually starts leaking. That's the entire reason CO2 guns have a cartridge-oiling ritual that PCPs don't need.
The oiling routine that actually works
- Use silicone oil only. Crosman Pellgunoil and RWS Chamber Lube are both widely available and built specifically for rubber and synthetic airgun seals.
- One drop on the cartridge tip, right where it meets the piercing pin, before you screw it in.
- Let the gas flow do the work. As the cartridge pierces and gas moves through the gun, it carries that drop of oil past every seal on its way to the valve, which is why a separate internal oiling step usually isn't needed for a gun in regular use.
- Never substitute petroleum-based oil. Umarex is direct about this: ordinary gun oil reacts with silicone seals roughly the way gasoline reacts with styrofoam, and it will shorten seal life rather than protect it.
| Habit | Effect on seals |
|---|---|
| Oil every fresh cartridge with silicone oil | Keeps piercing seal and o-rings supple; the standard, low-effort routine |
| Leave a pierced cartridge in for weeks | Constant compression wears the seal faster than periodic use |
| Use petroleum-based household or gun oil | Degrades rubber/synthetic seals over time |
| Store the gun completely dry, never oiled | Seals can stiffen or shrink slightly from disuse |
| Shoot in freezing temperatures without adjusting expectations | Doesn't damage seals directly, but drops velocity and point of impact |
Storage: don't leave it charged for the long haul
If you're setting a CO2 gun aside for more than a day or two, fire it dry or release the cartridge rather than leaving it pierced and pressurized. The logic is the same as not leaving a car parked with the parking brake engaged for months: constant load on a seal that's designed for cyclical use accelerates wear. For actual long-term storage (weeks or months), remove the cartridge entirely, wipe the gun down, and store it somewhere dry. If you also run a PCP, the same "don't leave it at either extreme" logic applies there too, just for a different reason: a PCP wants some air left in it, not none, to protect its valve seal.
Cold weather: the seals are fine, the velocity isn't
CO2 pressure is a direct function of temperature. As the liquid CO2 inside the cartridge cools, the vapor pressure driving each shot drops with it, and so does muzzle velocity. This isn't a leak or a maintenance failure, it's basic physics, and it's the main reason serious CO2 shooters keep cartridges warm (a jacket pocket, not a car trunk) before a cold-weather session. A PCP, running on compressed air rather than a gas near its phase-change point, is far less sensitive to temperature and holds its numbers much better in the cold. If consistent cold-weather performance matters to you, that's one real argument for stepping up to a regulated PCP; see how PCP regulators keep power consistent for what that buys you, and pellet gun vs PCP for the fuller cost-and-capability comparison between the two paths.
Keep the seals happy
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If a CO2 gun starts shooting inconsistently even after a fresh, oiled cartridge, the troubleshooting path is the same one PCP owners use for a suspect valve: chronograph a string and see whether the spread points at a seal problem. Diagnosing inconsistent shot strings →
FAQ
What oil should I use on a CO2 airgun?
A silicone-based oil made for airguns, such as Crosman Pellgunoil or RWS Chamber Lube. Ordinary petroleum-based household oil or firearm gun oil degrades rubber and synthetic seals over time and should never go near a CO2 gun's o-rings.
How often should I oil a CO2 gun's seals?
A drop on the tip of each fresh CO2 cartridge before you install it is the standard routine, and for a gun shot regularly that's usually enough. The gas flow carries the oil past every seal it needs to reach on the way to the valve, so there's rarely a need for a separate oiling step.
Should I leave a CO2 cartridge in the gun between uses?
No, not for extended storage. A pierced cartridge keeps the piercing seal and internal o-rings under constant pressure, and seals that stay compressed for weeks wear out faster than ones that get periodic relief. Fire the gun empty or release the cartridge if you're setting it aside for more than a day or two.
Why does my CO2 gun shoot slower in cold weather?
CO2 pressure is a direct function of temperature, not a fixed number. As the gas cools, pressure drops, and so does the velocity behind every pellet. Expect a meaningful drop as temperatures approach freezing; a PCP, which relies on compressed air rather than a phase-change gas, doesn't have this problem to nearly the same degree.
Can a CO2 gun's seals dry out from sitting unused?
Yes. Rubber and synthetic seals can shrink or stiffen slightly with long periods of no lubrication at all, which is part of why an occasional drop of silicone oil on a cartridge, even during light use, keeps a gun sealing reliably rather than developing a slow leak the first time it's fired after months in a closet.
What causes a CO2 gun to suddenly lose gas or leak?
Most often a worn or dirty piercing seal, a cartridge that wasn't seated fully before the piercing screw was tightened, or a seal that's gone dry from petroleum oil contamination. Reseating a fresh cartridge carefully and switching to silicone oil solves the majority of slow leaks.
Does CO2 damage seals that PCP air doesn't?
The cold itself is the difference. Piercing a cartridge briefly exposes the piercing seal to very cold, rapidly expanding gas, which is harder on a seal over thousands of cycles than the room-temperature compressed air a PCP uses. That's exactly why CO2 seals need the cartridge-tip oiling routine that PCP fill probes don't.
How long do CO2 gun seals typically last?
There's no fixed number; it depends on shot volume, oiling habits, and storage. A well-oiled gun that isn't left charged for long stretches between sessions can go years without a reseal, while a dry, constantly-pressurized one can start leaking much sooner. Watch for a fill that empties faster than it used to, which is the usual early warning sign.
