When you start researching air compressors, whether you’re shopping for a new one or troubleshooting your old one, the first thing that may strike you is the difference between oilless and oil air compressor models. What exactly is the difference? And which one should you choose?
Here’s a look at the main differences between oil or oilless air compressor units and who should buy which type. Each one has advantages and disadvantages over the other.
What is an Oil Air Compressor?
Like a reciprocating engine, an air compressor uses a moving piston inside a cylinder to draw in air and then compress it. Instead of igniting the air with fuel and spark, the compressed air is sent into your air tank, where it’s held at high pressure.
All that moving around of the piston inside the cylinder causes a lot of heat and friction. That leads to wear and tear on the item, which isn’t good. Eventually, the piston seals will wear down, and the cylinder will make less air pressure than it was designed to do.
The best way to solve the problem is with lubricating oil. This is precisely like having oil in your car, and for the same reason. It reduces heat and friction. What heat is built up, the oil wicks away from the pump case and the cylinder.
Only by ensuring that the proper amount of oil gets into the cylinder and piston will the pump operate the way it should. The main difference between oilless and oil air compressor units is this oil and the need to make sure that it is there. It also means that the operator will need to change it occasionally, which means more maintenance.
What is an Oilless Air Compressor?
Having an oil system built-in to lubricate the pump adds weight, complexity, and cost to the air compressor. Wouldn’t it be great if they could find a way to forego all of that? Well, they have—enter the oilless air compressor.
Instead of using oil, these units use a Teflon lining inside the cylinder to reduce heat and friction. It works fine and is basically maintenance-free. The system works great on smaller compressors, and on units that aren’t used very much.
But when comparing an oil vs. oil-free compressor, it’s important to think about the differences. Oil-free compressors are suitable when you need a smaller unit that is more portable. They aren’t built for constant-duty cycles—oilless units are best for home users where use is occasional.
The Main Differences Between Oilless and Oil Air Compressors
Besides the obvious difference between the two in terms of the lubrication system, oilless and oil air compressors function in the same ways. Both styles are available in a variety of sizes and CFM ratings. Picking the right unit for you comes down to looking at how you’re going to use the compressor and how much maintenance you’re willing to do.
The fact that oil air compressors have lubricating oil in them means that there is more maintenance involved. The oil will have to be changed eventually, even if it doesn’t happen very often.
If you’re in the market for a larger air compressor, chances are the difference in performance between lubed and oil-free compressors more than makes up for the small difference in the extra maintenance. If you choose between the two compressors of the same size, you’ll have to investigate further.
Oil-lubed compressors are the go-to models for shop and factory use where maximum performance for a long lifespan is required. These machines are bigger and bulkier than oilless compressors, but in these cases, the users value the machinery’s long service life.
Oil-free compressors are smaller units made for occasional use and are ideal for home use or DIY-ers looking to benefit from pneumatic tools in their workshops. They aren’t designed to operate 24/7, and most people who buy them don’t want to do that anyway.
All of that might make the oil-free compressor sound like a bad deal—which it is not. Oil-free compressors provide years of reliable use under the right conditions. They’re smaller, lighter, and more portable than oil air compressors. For workers traveling or moving from job site to job site, an oilless unit is just right.
Having an oil-lubed compressor puts some limitations on your use of it as well. Oilless compressors are generally more portable since they can be laid down on their sides for easier transport. You can’t do that with an oil compressor since the oil would wind up getting where it shouldn’t.
Oil air compressors will cost more than a similarly-sized oil-free compressor. Why? Because the oil-lubed system is a little bit more complicated for the manufacturer, so production costs are higher. It’s also a more durable good since the lifespan of the unit is greater. That means that while it costs more initially, it will last longer and will be many years before it needs to be replaced.
The circulating oil in an oil air compressor does more than just dissipate heat and lubricate parts. It also acts as a sound barrier. Oilless compressors are noisier than oil units for several reasons.
For one thing, oilless compressors are usually smaller and have less mass than larger units. That means that their cylinders banging around are more likely to cause vibrations over the entire unit, resulting in more noise. Another thing about these units is that they are built lighter—the cylinders have thinner walls, and the pump case is attached with smaller bolts. These little things total up to mean that compared to comparable oil air compressors, the oilless models are noisier.
All compressors vary their noise level depending on how hard they are working. But you’ll hear a lot more variation in an oilless compressor, where there is little between the working piston and your ears.
The noise a compressor makes is an important decision criteria when you’re out shopping for a new air compressor. Some shops are loud. If you’re working in your garage, and there’s little insulation, the sound of a noisy air pump can travel right through the walls into the house. Inside the garage, with the thin metal door and the sound reflecting off of the cement floor, the sound of a compressor can get tiring fast.
Should I Choose an Oil or Oilless Air Compressor?
So which type of air compressor is right for you and your workshop? To figure out the answer, you’ll need to take a hard look at exactly how you’ll use your new air compressor and how often.
An excellent place to start is the owner’s manuals for the two compressors. Each manufacturer will have them available for download on their websites. Just download them and briefly look at what is involved in keeping it running. The oil-lubed unit will likely cost more, but it will also have a longer service life. Is that worth it for your use, or are you going to use it so little over the years that either one will basically last forever? Everyone’s use is different, so only you can tell which is right for you.
If you’re on one end of the user spectrum or the other, the choice is easier. If you’re an industrial user who plans to use their compressor continuously, or you run a large shop or factor with many users, you’ll want an oil-lubed compressor. On the other end, if you’re a home user just looking for something to inflate a tire or use a nail gun once a year, you’ll want an oilless compressor.
It’s users in between these two that will need to really compare the difference between oilless and oil air compressor.
Both types of air compressors can provide decades of reliable service as long as they are cared for properly. Knowing which kind you have is the first step to maintaining it well and to troubleshooting it if something goes wrong.