How Many Drops of Oil in an Air Tool?

Two answers circulate. One says "two or three drops a day". The other says "a few drops every hour". Both trace to real manuals, and the gap between them is not a disagreement. The makers count on different clocks. Some count per day, some per hour of steady running, and some per hour of trigger time. The dose also grows with the tool. A small 1/2 in impact gets 4 or 5 drops. A 1 in impact that needs 60 CFM gets 8 to 12.

So the answer is the figure your maker prints, read with its clock. Where the maker prints no number, the documented range for impact wrenches is 4 to 12 drops at the inlet before use. That range is ours, built from the table below.

What "oiling an air tool" means

An air tool runs on an air motor. Compressed air comes in at the inlet, turns the motor, and leaves through the exhaust. Oiling means putting a light oil into that inlet, so the air carries it through the motor. Ingersoll Rand describes it that way: you add the oil, reconnect the air, and "run the tool for a few seconds to distribute the oil through the motor."

Air tool oil is the light oil made for this job. Jet allows SAE #10 oil or sewing machine oil in its place. Chicago Pneumatic names SAE #10 for its lubricator.

An inline lubricator (Jet calls it an in-line oiler) does the same job without your hand. It sits in the air line and drips oil into the passing air at a set rate. Ingersoll Rand draws it as the third part of a filter, regulator and lubricator unit, mounted before the hose.

The impact mechanism is the other part that needs lubrication. That is the hammer and anvil at the front of an impact wrench. Ingersoll Rand says it "requires separate lubrication from the air motor", mostly grease. Inlet oil does not reach it. Keep the two apart, because a lubricator replaces only the first.

A drop is not a unit in any of these documents. No maker gives its volume. So drop counts compare well between makers, but not to the decimal.

What the makers print, tool by tool

Five tools from four makers, read from ten of their documents side by side:

Ryobi's RAIW12 manual adds a fifth maker, with no number: "a few drops of air tool oil" at the inlet, daily.

Three things stand out. Only two of the five tools have a printed drop count for hand oiling. Only two have a printed lubricator rate. And no tool here has both.

Why the numbers differ

The clock is different

Jet counts in days and in hours of steady work. Its manual says the wrench "should be lubricated daily (or before each use)". It then adds: "During continual operation, it should be re-oiled every 1 to 2 hours."

Ingersoll Rand counts in hours of use. Its 2922 and 2015MAX sheets show each service as a circle with a time inside, and define "h=hours, d=days, and m=months of actual use." Both drawings put the oil can at the inlet on 8 h. Ingersoll Rand spells out what a running hour means in its 2922 grease note: it is "the amount of time the tool's trigger is pressed", not hours on the wall clock.

Eight hours of trigger time is a lot. An impact wrench used in short bursts may take several working days to log it. That is why Ingersoll Rand pairs the 8 h mark with a before-each-use dose on its 2922 page. The dose covers the start of each job, and the 8 h mark covers long running.

Chicago Pneumatic counts in days. For the CP7748 it says: "If an air line lubricator cannot be used, add air motor oil to the inlet once a day."

The tool is different

The 2922 is a big tool. Ingersoll Rand lists it with a 3/4 or 1 in drive, a 1/2 in minimum hose and a 60 CFM air requirement. The Jet JAT-102 is a 1/2 in drive on 3/8 in hose, rated at 4 CFM average. More air through a bigger motor gets the bigger dose: 8 to 12 drops against 4 or 5.

Do not turn that into drops per CFM. The 60 is Ingersoll Rand's requirement and the 4 is Jet's average, so they are not the same kind of figure. Our air hose guide shows how far apart an average and an at-load figure can sit: 6.2 against 25 SCFM on one Chicago Pneumatic wrench.

The method is different

A hand dose is a count you put in once. A lubricator rate is a flow, in drops per minute. The two are not on the same scale, as the walkthrough below shows. A forum answer of "a couple of drops" may be someone reading a lubricator rate as a hand dose, or the other way round.

Walkthrough: one day, by hand and on a lubricator

Take the Jet JAT-102, since its manual gives the fullest hand schedule. Suppose a day where the wrench runs steadily for 4 hours in total. Here is what each method adds up to, worked from the printed figures. Nothing here was measured.

By hand, on Jet's schedule:

1. Before use: 4 or 5 drops.
2. During the 4 hours: re-oil every 1 to 2 hours. Every 2 hours gives one top-up, at the 2 hour mark. Every hour gives three, at 1, 2 and 3 hours.
3. After use: Jet says to add 4 to 5 drops again, run it briefly, and disconnect.

That is 3 to 5 doses of 4 or 5 drops: 3 x 4 = 12 drops at the low end and 5 x 5 = 25 at the high end.

On a lubricator. Jet allows an in-line oiler but prints no rate for it. So borrow the rate Chicago Pneumatic prints for its CP7748, also a 1/2 in impact: two drops a minute. Over 4 hours of running:

4 h x 60 min x 2 drops = 480 drops

At the lower end of Top Cat's 1 to 2 drops a minute, it is 4 x 60 x 1 = 240 drops.

So the lubricator puts in roughly 10 to 40 times what the hand schedule does: 240 against 25 at one end, 480 against 12 at the other. That is not an error by either maker. A lubricator feeds the motor all the time it runs. A hand dose is a film put in at the start and topped up.

What it means for you: the hand count is not a lubricator setting. Setting an oiler to "4 or 5 drops" means nothing without a time. Set it to the per-minute rate your tool's maker prints. If the maker prints none, the two published rates here are 1 to 2 drops a minute.

The no-detergent rule

Jet states it flat: "Do not use detergent oil." It gives two substitutes for air tool oil: "SAE #10 oil or sewing machine oil".

Jet does not give the reason. Ridgid does, in the manual for its R350PNA air nailer: "Do not use detergent oil or additives as these lubricants will cause accelerated wear to the seals and bumpers in the tool, resulting in poor tool performance and frequent tool maintenance." AIRCAT, through Florida Pneumatic, asks for "a petroleum-based non-detergent air tool oil with a rust inhibitor."

So the choice is the oil your maker names, a bottle sold as air tool oil, or one of Jet's two substitutes.

The makers here name these:

• Jet: air tool oil, or SAE #10 or sewing machine oil.
• Ingersoll Rand: IR #10 Air Tool Oil, for the 2922 and 2015MAX.
• Chicago Pneumatic: SAE #10 oil in the lubricator, and it recommends CP Oil Protecto-Lube.
• Top Cat: "A light grade oil such as Mobil DTE light or equivalent."

Ingersoll Rand also sells IR #10 with antifreeze, for work that calls for it. Ridgid's manual allows air tool lubricant or ethylene glycol antifreeze as a cold weather oil, and warns that "some commercial air line drying liquids are harmful to 'O' rings and seals."

What an inline lubricator replaces, and what it does not

It replaces the drops at the inlet. Ingersoll Rand's 2922 setup page says to add the 8 to 12 drops "unless the air system uses an appropriate inline lubricator." Chicago Pneumatic says to oil by hand only if a lubricator "cannot be used." Jet says lubrication "can be done with an in-line oiler, or manually." Ingersoll Rand's general guide says the same: re-oil during long use "when an inline lubricator is not being used."

It does not replace the grease. Ingersoll Rand's general guide says the impact mechanism "requires separate lubrication from the air motor". The grease schedules printed here:

Jet adds a separate weekly job: "Remove set screw from oil inlet (Figure 1) and insert several drops of air tool oil weekly." The manual does not name the part that inlet feeds. It is not the air inlet, though, so a lubricator does not reach it either.

It does not replace the dose before storage, as some makers write it. Top Cat discusses lubricators and still says to put "a few drops of oil" straight into the inlet before storage. Ingersoll Rand's guide lists "before storing the tool to help protect against corrosion" among its oiling times. Jet's after-use dose plays the same part, and its storage rule is plain: "Always oil the tool and disconnect air hose before storage."

It needs its own service. Both Ingersoll Rand drawings mark the lubricator with a 48 h circle and an oil can. That reads as a check of its oil supply every 48 hours of use. The filter drain is marked 24 h, and the text says to drain condensate from the filter and tank daily.

A lubricator also adds a fitting to the air line. Our air hose guide notes the hose industry's warning that fittings and restrictions add pressure loss, and an inline oiler is one more.

Where this answer stops applying

• Other tools. Every figure here belongs to the tool it was printed for. A grinder, a die grinder or a nailer is a different machine. Ridgid's nailer manual is cited only for the reason behind the detergent rule.
• No drop size. None of the makers says how big a drop is. The 10 to 40 times comparison counts drops, not millilitres.
• The minute is not defined. Chicago Pneumatic and Top Cat give lubricator rates per minute but do not say whether that is minutes of air flow or clock time. The walkthrough counts running minutes only.
• Reading the drawings. The 8 h, 10 h, 24 h and 48 h marks come from Ingersoll Rand's pictures, read against its own key. The 2015MAX sheet prints no number of drops, and this page does not supply one.
• Air quality comes first. Jet asks for "clean, dry air" and a daily tank drain, and warns that "water in the air line may enter the tool and cause damage." Ingersoll Rand asks for a daily drain of the filter and tank. Oil does not fix water in the line. Tank draining and compressor sizing are covered in whether a bigger tank gives you more CFM.
• Power loss has other causes. Ingersoll Rand's 2922 troubleshooting page lists low air pressure at the tool before lubrication. A dry motor is one cause of a weak wrench, not the only one. If the problem is a stuck nut, read nut-busting against fastening torque before blaming the oil.

Storing an oiled air tool

The last dose of the day is also the storage dose. Jet, Ingersoll Rand and Top Cat all tie oiling to putting the tool away, and Ingersoll Rand asks for "a clean, dry location." Jet also warns against storing the wrench "in very humid locations which promotes rusting of internal mechanisms."

Oil inside the tool will weep a little. Ingersoll Rand says lubricant building up around the spindle, reverse ring and trigger is normal for a short time after maintenance, and to wipe it off. So keep air tools on their own shelf or drawer, not loose on top of hand tools you want dry. Moisture is the bigger risk in a garage, and rust prevention in tool storage covers keeping it out.

If you also run a nailer off the same compressor, its air use is worked out per nail in the framing nailer CFM guide. Check that manual for its own oiling rule before sharing a lubricator.

The thirty-second check

1. Find the oiling line in your tool's manual. If it gives drops and a time, use both.
2. Note the clock. "Daily", "before each use", "every 1 to 2 hours of continual operation" and "8 h of actual use" are four different schedules.
3. No number printed? The impact wrench hand doses printed here run from 4 or 5 drops (Jet, 1/2 in) to 8 to 12 (Ingersoll Rand, 3/4 and 1 in).
4. On a lubricator, set a rate per minute, not a count. Chicago Pneumatic prints 2 drops a minute and Top Cat 1 to 2.
5. Use air tool oil, SAE #10 or sewing machine oil. Never detergent oil.
6. Grease the impact mechanism on its own schedule, lubricator or not, and oil the inlet before the tool goes into storage.