Oil vs. Oil-Free Air Compressors: Which is Better?

Of all the criteria that go into selecting an air compressor, none are subject to more debate than whether to go with oil-lubricated or oil-free. Unfortunately, it can be hard to cut through the noise and get to the bottom of which one is better. The truth is, they both have their advantages and drawbacks and either one may be better for some people but not for others. 

So in this article, I’ll give you a side-by-side comparison of oil-lubed and oil-free air compressors so you can make an informed decision. I’ll start with a brief description of each, then look at how they compare in key areas. Finally, I’ll recap with a list of pros and cons for each type.

What Is an Oil-Lubricated Air Compressor?

As the name suggests, an oil (aka oil-lubricated) air compressor uses oil for lubricating and cooling the moving components in the compressor’s pump. This helps prevent overheating and mitigates wear and tear. Oil-lubed compressors are typically larger and used more for heavy-duty applications.

Most compressors employ splash lubrication, in which oil is continuously splashed up onto the crankshaft and cylinder walls by small dippers during operation. Some compressors use pressure lubrication, in which oil is pumped to key areas – but these are less common (and significantly more expensive).

What Is an Oil-Free Air Compressor?

In an oil-free air compressor, the moving pump components are coated in friction-reducing materials such as Teflon. This reduces wear and mitigates heat without the use of liquid oil. Oil-free compressors are typically lighter-duty and are the most common type of household compressor.

Now, let’s delve into their key differences by comparing the two types according to individual criteria.

Operation/Applications

The best place to start when comparing oil and oil-free compressors is with usage, especially since this is one area where they diverge significantly.

Oil Air Compressors

Oil-lubricated air compressors typically win the day in terms of the higher CFM output they can provide. This is because they usually operate at higher RPMs compared with oil-free models of the same size.

In general, they are also considered superior for continuous-use applications where the pump will be running for long periods, such as painting, automotive repair, or cutting and grinding. This is why they’re the preferred choice in many professional/industrial settings.

Oil compressors do have some limitations in terms of the settings and applications they can be used for. One such limitation is extreme cold – the oil can become thicker at cold temperatures, which makes startup more difficult. Some compressors use all-season or multi-viscosity oils such as 10w30 to combat this, but this is not always the case. 

The oil itself can also contaminate the compressed air supply, making this kind of compressor unsuitable for certain applications – but we’ll get into that a little later. 

Oil-Free Air Compressors

Oil-free air compressors typically have a lower CFM output than their oil-lubed counterparts of the same size, which is why they are more commonly used for tasks that don’t require a lot of continuous operation. 

Depending on the size of the compressor, this can also limit the range of pneumatic tools that can be used with them, as many of the heavier-duty air tools (such as large impact wrenches and framing nailers) have a high CFM demand. For this reason, oil-free compressors are more commonly found in homes or as part of a contractor’s toolkit.

Oil-free compressors do have an advantage in terms of portability. For one thing, they are typically lighter and more compact than oil-lubed models. But more importantly, they can be transported on their sides without fear of oil spilling, leaking, or getting into places it shouldn’t be within the pump itself (though there are still other risks to consider when placing any compressor on its side).

And with no oil to become “sludgy” from low ambient temperatures, oil-free compressors can be used in cold weather with no problem. Indeed, they tend to do well at virtually any temperature (within reason).

Air Contamination

Another factor to consider in terms of usage is the potential contamination of your compressed air with oil or harmful pollutants.

Oil Air Compressors

In most reciprocating air compressors (the most common type), air is drawn into the pump cylinder and compressed by a piston moving up and down inside the cylinder. With an oil-lubed compressor, the oil below is kept out of the air chamber by piston ring seals, but some oil will inevitably escape into the chamber in the form of vapor. One or more filters or air/oil separators sit downstream of the compression chamber to capture this – but it’s not always 100% effective.

A small amount of oil contamination may not seem like a big deal in some applications, but in others, it can be a very big problem. Food production facilities, for instance, must have zero chance of contamination, for obvious reasons. But even if you’re using the compressor for a quick paint job, the oil can mix with the paint and ruin your finish.

While very rare, another thing to consider is that if the oil gets very hot, it may emit carbon monoxide, which can be a deadly form of air contamination. 

Oil-Free Air Compressors

Since they contain no oil, oil-free compressors carry virtually no risk of air contamination from oil vapor or carbon monoxide (unless they are being operated near a separate source of CO such as vehicle exhaust). If you intend to use your compressor for breathing air (filling scuba tanks, etc.) or anything else that requires zero contamination – or you just don’t want to risk oil interfering with your craft painting projects – you’re better off with an oil-free compressor.

Maintenance Requirements

One of the biggest differences between oil and oil-free compressors is how much maintenance they require.

Oil Air Compressors

Just as you do for your car or lawnmower, you’ll need to change your air compressor’s oil periodically and keep it at the appropriate level at all times. You’ll also need to replace the oil filters and air/oil separators at regular intervals. Some models also use a drive belt, which you may need to re-tension and replace on occasion.

How often you perform these tasks will depend on the manufacturer’s recommended service schedule, but you can count on doing a fair bit more maintenance on an oil-lubed compressor than you would on an oil-free model.

Oil-Free Air Compressors

Make no mistake, there are still maintenance tasks to perform on an oil-free compressor (changing the air filters, draining the storage tank after every use, etc.), but they are generally very low-maintenance. The “self-lubrication” coating on the pump components is typically designed to last the lifetime of the compressor itself, so you’ll never have to worry about that.

Durability & Lifespan

The common wisdom is that oil air compressors hold up better and last longer than oil-free compressors. This is largely a holdover from the early days of oil-free compressors when the technology was still young – but there is still some truth to it.

Oil Air Compressors

While it may not be fair to say that all oil-lubed compressors are more durable than oil-free models, they do have the potential for it. 

Oil does a great job of protecting the pump components from excessive heat and minimizing normal wear and tear. And since the oil can be kept clean and fresh with regular oil changes, it can do its job effectively for many years. Most air compressor oil also contains additives to protect against corrosion and rust. 

The expected lifespan of an oil-lubed air compressor is anywhere from 10-15 years (for a reciprocating model – rotary compressors often last 20-30 years). But many people claim to have been using the same oil-lubed air compressor for over 30 years and still swear by it.

Ultimately, the longevity and durability of your compressor will largely depend on how well you maintain it – and with the extra maintenance requirements of oiled compressors, it becomes increasingly important to stay on top of it.

Oil-Free Compressors

The expected lifespan of a reciprocating oil-free compressor is around 10-15 years (again, rotary models typically last longer). Of course, keeping up with maintenance will make a difference, as will how much you use it. The lubricant coating on the internal components will eventually wear out and can’t be replaced like liquid oil can – but it will take a long time if you take proper care of your compressor and limit its exposure to moisture.

Since most oil-free compressors aren’t typically designed for continuous use, you may not rack up as many hours of use as you would on an oil-lubed model. In this regard, oil-free compressors may not have the longevity of their oil-lubed counterparts in terms of actual hours of service – even though the number of years may be about the same.

Noise Levels

It’s often been said that oil-free compressors are much louder than oil-lubed compressors, but again, this isn’t necessarily true of all of today’s models.

Oil Air Compressors

For the most part, oil-lubed compressors tend to run quieter. Oil can act as a noise dampener as well as a lubricant, which is one reason oil-lubed compressors are said to be quieter. These compressors are typically also more massive and have more material surrounding the pump, which can help reduce noise and vibration. However, they also typically run at a higher RPM and have more horsepower than oil-free models, which can make them plenty loud.

Oil-Free Air Compressors

Typically made from lighter materials and designed to be more compact, most oil-free compressor pumps offer little in the way of a barrier between the pump and your ears. However, many run at lower RPMs, which makes them run quieter. More and more manufacturers are also designing their oil-free compressors with advanced noise reduction technology to keep them quiet. All in all, while the majority of oil-free compressors can be louder than oil-lubed models, the difference isn’t usually very big – typically around 5-15dB.

Cost

When comparing air compressor costs, it’s crucial to keep size in mind. Oil-free compressors typically come in smaller sizes than oiled models, though there are plenty of large stationary oil-free compressors out there. It’s also good to consider the long-term costs as well as the upfront investment.

Oil Air Compressors

Without a doubt, oil-lubricated air compressors are usually the more expensive of the two types. This is partly because they require somewhat more complex manufacturing and are made from more expensive materials. But it’s also because they involve more maintenance costs. The cost of compressor oil, oil filters, and air/oil separators can add up over time. Of course, since all that maintenance will extend their lifespan, this may offset in the long run.

Oil-Free Air Compressors

In general, oil-free is the way to go if you’re looking to save money. They are typically made from relatively inexpensive materials and marketed primarily towards DIY-ers and general contractors rather than industrial interests, which helps keep the price down. They are also extremely cheap to maintain (only the intake filter needs to be changed). They may not be able to provide as many solid hours of service as an oil-lubed compressor, but 10-15 years of general use isn’t bad for the lower investment.

Oil-Lubricated Air Compressor Pros & Cons

To recap, here are the advantages and disadvantages of oil-lubricated air compressors.

Pros

  • Usually more powerful – higher CFM output & horsepower rating.
  • Better for heavy-duty & continuous-use applications.
  • Tend to be more durable and long-lasting.
  • Are typically quieter.

Cons

  • Higher upfront & maintenance costs.
  • Require more maintenance.
  • Aren’t ideal for cold temperatures.
  • Compressed air supply may be contaminated by oil/toxic fumes.
  • More difficult to transport due to weight and risk of oil leakage.

Oil-Free Air Compressor Pros & Cons

Now let’s look at the advantages and drawbacks of oil-free compressors.

Pros

  • More portable/easier to transport.
  • Better for use in very cold temperatures.
  • Cleaner compressed air supply.
  • Require very little maintenance.
  • Lower cost.

Cons

  • May not last as long in terms of overall service hours.
  • Most models are comparatively loud.
  • Typically not as powerful – lower CFM output.
  • Not ideal for heavy-duty & continuous-use applications.

In Conclusion

At the end of the day, there’s no clear-cut answer as to which type of air compressor is better for you. It ultimately depends on what you’ll be using it for and what your priorities are. Also, keep in mind that many brands have compressors that don’t fit entirely into the general parameters above, so it pays to look at the many models available and see how they compare. But I hope this article has given you a solid foundation to stand on! Thanks for reading!

Justin

Justin is a full-time blogger with a passion for anything DIY. When he's not hanging out with his wife and son, you can find him putting the finishing touches on yet another home project he's taken on. He's also the creator of AllAboutAirCompressors.com.