There's often confusion about oil-lubricated versus oilless air compressors.
With air compressor technology changing every year, many homeowners and professionals are left wondering what's outdated and what's still true.
So, let's get to the bottom of the oil vs. oil-free debate. For the sake of simplicity, we'll focus on reciprocating single-stage air compressors, since those are the most common types found in common applications.
All compressors, regardless of their type, need lubrication to moderate heat, friction, and the wear down of the pump and critical components. The biggest difference, however, is whether the lube comes from oil or a special material coating.
Oilless compressors do not use oil for lubrication. Instead, their wearable parts are coated in special friction-reducing chemicals and designed to be self-lubricating for the compressor's lifetime.
Splash lubrication is the most common type used in reciprocating single-stage air compressors. It works just how it sounds. These compressors use rotating dippers (think of small flat spoons) attached to the bottom of connecting rods that swing and splash oil up from the reservoir against the internal moving parts.
Comparing oil- and oil-free air compressors isn't so much about which is better as which is better for your application.
Oil air compressors are great for most non-sensitive applications. If you need to power mechanical tools in a garage or on the road, an oil compressor will serve you nicely. In fact, most mechanical air tools need a little bit of lubrication to work optimally.
Oilless air compressors are designed for delicate applications where you can't risk getting oil into the final product. For example, dentists use oil-free compressors to power their air tools so their patients don't get a mouthful of fossil fuel. Paint shops, breweries, and food processing facilities are other applications where oil-free operation is critical.
[NOTE] Breathing apparatuses require specific types of air compressors that are not carried by Air Compressors Direct.
Although application is the main factor that dictates the type of air compressor you'll need, there are some other basic differences between oil and oil-free air compressors that are summarized in the table below.
| Oil-Lubricated Air Compressors | Oil-Free Air Compressors |
|---|---|
| Oil stays in the air | Cleaner, dryer air |
| More maintenance required | Less maintenance required |
| Higher airflow models available | Less airflow on average |
| Louder performance on average | Quieter performance on average |
| Great for non-sensitive applications (mechanical tools) | Necessary for sensitive applications (paint tools, medical equipment) |
It's sometimes helpful to compare real-world examples. The table below compares four actual air compressors and their specs.
The first two columns compare two portable compressors that are exactly the same except one is oil and one is oilless. Similarly, the last two columns compare two stationary compressors that are exactly the same except for lubrication. This will give you an idea of the difference between oil and oilless, all else being equal.
| Oil vs. Oiless Comparison | 20 Gal. Portable Oil Lubricated | 20 Gal. Portable Oil-Free | 60 Gal. Stationary Oil Lubricated | 60 Gal. Stationary Oil-Free |
|---|---|---|---|---|
| Weight & Pump Drive Type | 200 lbs Belt Drive | 132 lbs Direct Drive | 261 lbs Belt Drive | 213 lbs Direct Drive |
| Pump Material | Cast Iron | Aluminum | Aluminum (Cast Iron Sleeve) | Aluminum |
| Max PSI | 135 PSI | 125 PSI | 135 PSI | 120 PSI |
| Max CFM | 5.2 @ 90 PSI | 6 @ 90 PSI | 12.8 @100 PSI | 10.6 @ 90 PSI |
| Noise Rating | 80 dBA | 53 dBA | 85-90dBA | 75 dBA |
As mentioned, there's often significant confusion about oil and oilless air compressors. Here are some myths we've busted.
Although routine maintenance and regular oiling did tend to make oiled compressors more durable in the past, this just isn't true anymore. Today's oilless compressors run cooler and come better protected than ever before.
While oil-free compressors were unquestionably loud in years past, today's designs feature sound-reducing technologies that make oilless compressors quieter, on average, than oil models.
Although oil-free compressors don't require oil changes, they still need some light maintenance. This includes replacing the air filter and cleaning/draining the drain valve if it's not automatic. Overall, though, oil-free compressors require less maintenance.
Ultimately, it's important to reiterate that the decision between oil and oil-free air compressors must come down to application and what you're trying to accomplish.
While the performance differences between these compressors were more pronounced in the past, today, each is designed to do its respective job well. In general, for sensitive air jobs, go with oilless. If the quality of the air doesn't matter, go with either.