Before using a lubricant, read the sections below that relate to the application you are using it for. Lubricants containing petroleum distillates (hydrocarbon solvents) or other flammable substances are not safe. They can end up in places where they won't evaporate before the gun is charged or fired. Combustion or explosion could result. WD40, many gun oils, cleaning solvents, silicone sprays and most similar products contain flammable chemicals. Many products intended for firearms are not safe for airguns. Substances with any significant toxicity should not be used. Not only could this be harmful with regular contact but these can become aerosolized and inhaled while charging or firing. Which lubricants are safe is explained below. Section 1 covers low-pressure CO2 and self-contained pump models. Section 2 covers high-pressure break barrel, PCP and HPA guns.
SECTION 1 : CO2 & SELF-CONTAINED PUMP
Crosman suggests Pellgunoil which works well in moderate temperatures. It comes in an applicator tube that contains 1/4 oz. Magnum Airpower's HIGH-PERFORMANCE AIRGUN OIL is less expensive and works better in all temperature ranges. It's available in 1/2 oz precision applicator bottles and 4 oz wide-mouth bottles.
It's a myth you shouldn't use petroleum oil for airguns. This myth stems from the common misconception that petroleum distillates and oil are the same thing. They are not, oil is what's left after the distillates are removed from crude oil. This subject is confusing to many because some distillates are commonly referred to as oil. The most common examples are heating oil and penetrating oil which are both petroleum distillates. The oil that is safe is called mineral oil also known as heavy oil. Mineral oil is not toxic or flammable. It protects against wear and corrosion better than silicone or natural oils, will not harden and doesn't become rancid. This is why all engine oils, including synthetics, are mineral oil based. It will not hurt the seals in your gun. Modern airgun seals are made of materials like Nitrile and urethane which are engineered for use with petroleum oils. I've been using mineral oil (engine oil) in airguns for many years and have never seen a Nitrile or urethane o-ring swell or dissolve.
It's a myth that engine oil is toxic. Most are not, some do contain potentially harmful additives, these will say so on the bottle and should be avoided. Used engine oil is more toxic and combustible, this is due to contaminants from fuel, combustion and wear.
It's a myth you shouldn't use detergent oil for an airgun. It actually works better than non-detergent. It has wear and corrosion inhibiting additives and helps remove moisture and contaminants as it works it's way through. An airgun doesn't experience the type of action or gain enough moisture for emulsion to be an issue.
Crosman Pellgunoil (Monolec GFS 8430) is SAE 30 engine oil with a high level of detergency. Because it is single viscosity it gets significantly thicker in cold temps. Magnum Airpower's HIGH-PERFORMANCE AIRGUN OIL is full synthetic and multi-weight. It flows freely in very cold temps and maintains it's viscosity in very hot temps.
Magnum Airpower's HIGH-PERFORMANCE AIRGUN OIL is non-toxic and provides the highest level of wear and corrosion protection in the industry. It works exceptionally well in all temperature ranges staying fluid at -40° F and maintaining the optimal SAE 30 viscosity at the highest possible environmental temps. It has an operating range of -40° F to 500° F with a flash point of 450° F. This oil is recommended for all self-contained pump and CO2 models. It also works exceptionally well for break barrel models that require petroleum-based oil. It can be used to oil all moving parts on all types of airguns. It should not be used in the compression chambers of PCP, HPA, dual-fuel or break barrel models that require silicone oil. For assembly and maintenance of such components use Magnum Airpower's HIGH-PERFORMANCE SILICONE OIL. Never use oil inside a HPA tank or on the internal threads of tanks or regulators. More about this in section 2.
SELF-CONTAINED PUMP : These models should be assembled with oil to lube all the seals and moving parts. Add a drop of oil directly into the pump chamber every couple hundred shots. You can do this more often if the piston isn't working smooth or produces inconsistent performance. If you accidentally over-oil you can fire the gun with the barrel pointed straight up, unloaded and safely away from you. In that position excess oil settles near the valve stem and blows out through the barrel. To prevent oil-lock, only use one pump for each shot until excess oil is cleared from the pump chamber and valve. A drop of oil should be applied to all pivot points of the pump lever and one at the back of the piston seal. This will lubricate the contact points of the pump assembly. The owners manual should indicate other model-specific lubrication points.
CO2 : Like the pump models above, these should be assembled using oil to lube all the seals and moving parts.
CARTRIDGE POWERED: For models with a piercing cap or rod that threads into the front of the gas tube, the threads should be oiled to keep them working smooth and prevent rust. A drop of oil should be placed on the tip of each cartridge before installation. For 22XX this prevents the piercing pin from getting stuck in the cartridge which keeps the cartridge stuck in the tube. It also lubricates the valve, ports and barrel to preserve performance and reduce corrosion. After installing a cartridge the gun needs to be fired once (unloaded) to pierce it. This is not a malfunction, it's how they are designed to operate. Other types of CO2 guns will pierce the cartridge automatically during installation.
BULK-FILL : A drop of oil should be placed in the fill nipple before each fill. This is not safe for dual-fuel PCP models. An explosion could occur during a rapid fill from an air tank. Refer to the PCP section below for more info.
SECTION 2 : PCP, HPA & BREAK BARREL
Magnum Airpower's HIGH-PERFORMANCE SILICONE OIL is non-toxic and highly resistant to rapid compression autoignition. With a flash-point above 586° F and autoignition temp above 900° F it's the safest on the market. It's an excellent compression chamber oil for break barrel models that require silicone oil. It's perfect for assembling high-pressure PCP components and can be periodically added through the fill nipple for maintenance. Crosman Silicone Chamber Oil (RMCOIL) is recommended by Crosman for their PCP guns. Magnum Airpower's HIGH-PERFORMANCE SILICONE OIL is a safer high-performance version. Both are dimethyl, phenylmethyl siloxane, trimethyl-terminated. Magnum Airpower's oil has a higher phenyl content which gives it a much higher flash point, better thermal stability and it's more hydrophobic to better prevent corrosion. This oil is available from industrial suppliers for around $450 per gallon and up. I sell it inexpensively to make it affordable for most. It has a viscosity equal to SAE 30, does not thicken in cold temps or thin in hot.
PCP & HPA : Without lubrication, PCP components can be difficult to assemble and o-rings are more easily damaged. Tanks are harder to install and remove without lubrication on the outer threads and o-rings. Many lubricants are not safe due to the risk of rapid compression autoignition. Use only lubricants that are recommended by the manufacturer or a trusted airgunsmith who works with PCP & HPA guns.
A drop or two of oil can be added through the fill nipple of PCP guns for maintenance. It works it's way through the system to prevent corrosion, prolong seal life and lubricate the valve stem. Many recommend never oiling PCP guns except during assembly. This is idiotic, all machinery works better and lasts longer with lubrication. I've been oiling PCP guns for many years and find it works extremely well to prevent rust, corrosion and reduce valve wear. To prevent over-oiling, every few-thousand shots is more than enough. After oiling, excess oil accumulation should be cleared. To do this, let the unloaded gun sit with the barrel pointed straight up for a few minutes. Then dry-fire it several times keeping the barrel pointed straight up. Keep the barrel pointed up through the entire procedure so the oil settles into the valve and shoots out through the barrel. Do this with the barrel pointing safely away from yourself and others.
No oil should ever be introduced into a HPA tank, regulator or the internal threads of either. They are commonly flash-filled, an explosion could result. Scuba tanks generally have grease on the internal threads to prevent corrosion. They are filled at slower rates so there is no risk of explosion when the correct type of grease is used. Grease works better than oil for this purpose, it stays in the threads where needed instead of settling and migrating the way oil tends to.
It's not high pressure that causes lubricants to detonate, it's rapid compression generated during a rapid fill. The fill rate required for rapid compression autoignition to occur varies by the type of lubricant and size of the container. A PCP tube capacity of 4.5 cubic inches would require a rate of about 2000 PSI per second for standard SAE 30 airgun oil to autoignite. The rate required for larger tubes is higher. The rate for smaller tubes stays about the same. Based on this it is safe to establish 2000 PSI per second as the minimum fill rate required to cause autoignition. The rate required for common silicone oils is about the same, for some specialty versions, like this one, it's much higher. Most silicone and SAE 30 petroleum oils are safe when there is no risk of accidental rapid fill. Only the safest type should be used otherwise.
BREAK BARREL : For most guns one drop of oil can be added as often as every couple hundred shots. Many will not require lubrication this often and some manufacturers recommend no oil at all. Some guns have a leather piston seal that needs to be oiled regularly. Some require petroleum-based oil and some require silicone-based. It's safest to fallow the manufacturers recommendation for which type to use.