The owner's manual for most air tools¹ has lubrication instructions: "place five or six drops of ... oil into the air inlet every day" seems standard for nailers; a grinder may take just one or two drops. To drive home the point, most toolmakers include a small sample bottle of oil with every tool they ship. The moisture in the compressed air has a nasty tendency to cause rust on the bearings and vanes in the air-powered tools, so they're especially prone to problems (even with an in-line filter). If you use continuous-flow tools like grinders or sanders, many toolmakers suggest an in-line automatic oiler (yep, got one).

Whether you do the "couple of drops a day" thing or spring for automation with the in-line oiler, that little bottle won't last forever. You can't use leftover 10W-40 when you run out, though: first off, it's hard to drip into those little tiny holes out of a quart bottle, and second it's too thick. Instead, you'll need to go back to where you got your tools and pick up a bottle of Air Tool Oil. In my case, that meant ducking into Sears the next time I was at the mall to buy a 4-ounce bottle of Craftsman brand. Craftsman air tool oil is a pale yellow, low-viscosity petroleum distillate² formulated to help dissolve gum and sludge while protecting against moisture. It's sold in a four-ounce bottle (SKU 918911) with a "flip-‘n'-drip" style cap; a style that makes it easy to squeeze just a few drops down the air inlet every time you unpack or re-pack a tool. It's also just right for dripping oil into the fill hole on my Craftsman 16309 Oiler.

Regular use of this product in your air tools is preventive maintenance against rust and the buildups of gum or varnish that reduce their performance. I never fire up an air tool without my inline oiler installed, and I always add a couple of extra drops to the tool when the job is done. The upside? they always have a protective coating of oil on their innards when I put them away after a day's work. The downside? There is none.


¹ except paint sprayers: for them, oil's a no-no.
² typical composition: 70-80% naphthenic hydrocarbons, 20-30% mineral spirits, 1% chlorinated hydrocarbons

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