An impact wrench is a tool powered by compressed air or electricity. The high-torque action of the impact wrench can loosen bolts or nuts -- such as those on vehicle wheel studs -- that would normally be very difficult, if not impossible to remove by hand with a ratchet wrench. Electric impact wrenches usually have a sealed motor, but air impact wrenches have moving parts that must be lubricated periodically.
Disconnect the air hose from the wrench by pushing the collar fitting on the air hose away from the tool while pulling the air hose straight out of the tool.
Hold the tool with the air inlet -- usually located in the bottom of the hand grip -- facing upward.
Squeeze the trigger and hold it in.
Squeeze one or two drops of light motor oil into the air inlet hole.
Release the trigger. Wipe up any spilt oil from the exterior of the tool with a rag.
To keep from having to manually oil your impact wrench, install an inline oiler between the air compressor and the air hose used to supply air to the tool. A small reservoir allows the right amount of lubricating oil to travel through the air line to the tool. Top off the reservoir with oil regularly to ensure the supply does not run out while using the impact wrench.
Use only sockets and extensions designed to be used with impact wrenches. Standard sockets and extensions can shatter if used with an impact wrench, possibly causing severe injury to the user and to bystanders. Never operate an impact wrench at a higher air pressure than the tool can handle. Consult the owner's manual to determine the wrench's maximum allowable air pressure.