If you have been researching the portable air compressors that are currently available on the market, you probably would have noticed that units come in two distinct configurations.
First, there’s the oil free electric compressor, and then there are also oil lubricated units. When considering an oil based compressor, many of your questions are probably in regards to the use of air compressor oil.
Oil-free air compressors are known for being relatively inexpensive, lightweight and portable, and of course their motors don’t require maintenance. Now this is not to say that buying an oil-lubricated air compressor means that you will need to be a mechanical engineer to run and maintain it.
In fact, an oil lubricated air compressor requires even less maintenance than a lawn mower. Besides being easy to maintain, oil lubricated air compressors provide a number of other compelling benefits.
The Benefits of an Oil Based Air Compressor
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• They last longer than oil-free air compressors. This is because oil based air compressors are more robust when it comes to lubrication. The cylinder in an oil-free compressor is usually lubricated by a Teflon coating.
Over time the coating will wear off, and this is why oil-free compressors won’t last as long. Using air compressor oil to lubricate a cylinder means that performance is maintained in extreme conditions, and a simple air compressor oil change will have a unit running like new again.
• Air compressors can be noisy machines. Most of the noise produced by an air compressor comes from the movement of the cylinder inside the motor.
This cylinder pushes the air that is then compressed inside the compressor’s storage tank. Oil-free units tend to sound quite abrasive, even if they are running at lower decibels.
In comparison, air compressor oil means that cylinder movement is smoother and produces a milder tone. This means that even at higher decibels, the frequency produced by an oil lubricated compressor will be more bearable for the average user.
• They are just as portable as oil-free units. We’ve reviewed numerous compressors on Power Tools Ninja. The lightest compressor we’ve seen so far has weighed in at 20 pounds.
That was the Senco PC1010. Compare that to the MAC700 which is three times the weight at 59 pounds. It looks a lot on paper, but in real world situations the portability is almost the same, especially considering they have a similar physical footprint.
The MAC700 is more powerful, and yes, it uses oil lubrication. So while oil-free units may come in lighter variations, it’s not a given that they will be easier to move around your work site.
Air Compressor Oil Does More than Just Lubricate
Of course, with these types of compressors being oil lubricated, the actual lubricants used will play a role in how efficient and durable a compressor is.
Besides lubrication, the oil in a compressor provides benefits like the ones detailed below;
• When air is compressed, it rises in temperature. This heat variation can produce excess moisture within the compressed air storage tank. The oil in a compressor pump lubricates while also cooling the air that is pushed through to the storage tank. This means less moisture buildup, and less chance of corrosion forming on metal parts.
• Oil is an effective sealant. Oil free air compressors require additional engineering to ensure that the motor runs at maximum efficiency. Even so, as the lubricated coating wears down within the cylinder, these oil free compressors become prone to air leaks.
Because oil doesn’t allow air to pass through, air compressor oil means that there are less leaks, and therefore more air can be stored per movement of the piston in the cylinder.
What Air Compressor Oil Type Should You Use?
You now understand the advantages of having an oil lubricated air compressor, but the question still remains; which air compressor oil type is right for you? You might also be wondering if there is such a thing as an air compressor oil substitute. For example, would it be possible to use standard motor oil?
Unfortunately there is no single air compressor oil that will work in all situations. The air compressor oil weight is determined by manufacturer specifications, and also by the climate where an air compressor would be used. If you purchase a compressor and live in a cold climate, you would have different oil requirements to someone who lives in a hotter climate. Always check manufacturer specifications first.
Here’s an example from the Makita MAC2400 Big Bore Compressor;
SAE 10W for cold climates ranging from -16 to 0 degrees Celsius, SAE 20W for 1 to 25 degrees, and SAE 30W for climates above 27 degrees.
As you can see, the air compressor oil weight varies depending on the climate. Remember that this won’t be the same for every unit, so confirm specific requirements in your user manual.
When it comes to air compressor oil alternatives, the simplest answer is that there aren’t any. While some very high grade motor oils will work, they’re not recommended because they contain detergents which will damage the seals in your compressor motor.
Always buy air compressor specific products, and if in doubt, check with your manufacturer for a recommended brand.
Here’s a nice video you can watch to get a better grasp of the types of oil that you can find on the market.
How Often Should Oil Be Changed?
Individual manufacturer specifications change, but generally an air compressor oil change should be performed between every 500 and 1000 operating hours. This may seem like a long time, but consider that we are dealing with small, single cylinder motors.
Regardless of manufacturer specifications, it’s important to check oil levels and oil color regularly. New oil will be a light amber color, while dirty oil will turn a darker brown and then black color. Your oil should never become this dark. Use the dipstick on your compressor, or the sight gauge on some models to determine the color and levels of your oil.
Remember, maintaining good quality oil in the compressor will ensure that it is efficient, and that it will last for many years.
Other Oil Accessories
For specific applications, an inline air compressor oiler may be required. This is a unit that you will attach to the airline, which then delivers oil to a pneumatic tool. Much like an air compressor, the oil requirements from an inline lubricator will change depending on the tool you are using.
With some compressors, an inline feed will also be used to lubricate the motor.
Most tools don’t require oil lubrication, and in fact will reduce in efficiency if air is mixed with oil.
To ensure that oil is filtered from the compressed air you are delivering to your tools, check that either your compressor has a built in separator, or install an inline air compressor oil separator between your compressor and your pneumatic tools.
Are Oil Lubricated Compressors the Best Choice?
Like we often say at Power Tools Ninja, there rarely is a ‘best’ choice. Your perfect compressor will depend entirely on your needs. A small oil-free compressor can take care of most light tasks, but as you approach heavier duty applications you will deal almost exclusively with oil based compressors.
Now that you know all about the difference between oil based and oil free air compressors, why not take a look at the options in our detailed Air Compressor Reviews section.