What is an Air Compressor?
In short, an air compressor is a device that stores energy in the form of compressed air, which can then be converted back to mechanical energy when using air tools. In its basic form, an air compressor has a storage tank, a motor, and pump. Typically this motor is either electric or powered by some type of fuel such as gasoline, diesel, or similar. A pressure switch will monitor the pressure of the air stored in the tank and will signal to turn the motor on when air pressure drops below a certain threshold. Similarly, once the air pressure reaches the maximum value, the pressure switch will shut the motor off.
Air compressors are typically ranked by how much air pressure they operate at. LPAC or low-pressure air compressors deliver up to 150psi and are the most typical for home garage use. There are also MPAC or medium pressure air compressors which operate between 150-1000psi and HPAC or high-pressure air compressors deliver more than 1000psi. The latter two would more so make sense if you run a professional outfit with sufficient pressure regulation and many people operating tools using the same central compressor.
When to Use an Air Compressor and Why
You use an air compressor any time you want to use air tools. Air powered tools, also known as pneumatic tools, can provide a vast variety of functions. Impact wrenches, paint guns, ratchets, drills, screwdrivers, sanders, and pressure washers are just some of the many types of air tools that require an air compressor.
While the automotive uses may be obvious, many people use air power to do many other household tasks such as inflating sports balls, inflating air mattresses, many kinds of paint work, power washing the driveway, roofing projects, and more. In general, having the ability to use air power can generally speed your work in the garage as well as around the house.
What A Home Auto Mechanic Needs
When it comes to automotive work, the most commonly used air compressors in most garages are going to be electric. The reason for this is that electric air compressors don’t use flammable fluids, and in general tend to be regarded as safer in confined spaces such as a garage for this reason. As such, we have limited this guide specifically to electric air compressors geared towards the automotive enthusiast. That said, within the realm of electric air compressors, there are quite a few different styles and geometries that will get the job done. Most of these are just different tank configurations and shapes that lend themselves well to various tank capacities and storage configurations.
PSI and Tank Capacity
A common mistake when buying an air compressor is to consider the PSI in isolation of other features. While PSI is relevant, it’s not necessarily the most important feature by itself. PSI works in concert with tank capacity to ultimately determine storage capacity for air. PSI, or pounds per square inch, is a measure of pressure. Tank capacity is a measure of volume. The higher your pressure and the higher your volume, the higher the total storage capacity for air.
Why do you want storage capacity as a home mechanic? It’s simple. Every time you use an air tool, you use a large amount of air. If you were to rely solely on your pump to provide this air in real time, it may not be able to keep up. Having stored air allows your pump to work to supply you with air in between times you are using your tools. The more storage capacity you have, the less likely you are going to overwhelm your pump and have to wait for air pressure to build back up.
When it comes to tank capacity, it is best to err on the larger side to accommodate as many tools as possible. This will allow you to run most tools for a decent amount of time. For intermittent use, 5 gallons is a good starting point if most of your work is inflating tires, operating an impact gun, and other activities related to working on your car. If you intend to spray paint, sand, use a grinder, or use other tools that are on for significant amounts of time continuously, you may want to upsize considerably or you will find that your compressor has to occasionally catch up.
Flow
Air flow, often measured in cubic feet per minute (cfm), refers to how much air your pump can deliver in real time. This measurement is commonly represented as cfm at 90psi, as the air flow will vary depending on the pressure in your tank.
The easiest way to determine what cfm rating you require is to look at your air tools to determine which has the highest demand. For reference, an average 1/2″ impact wrench typically requires between 4-6 cfm. A compressor that can provide 6cfm at 90psi will be able to power the average impact wrench indefinitely without having to stop to wait for your tank to repressurize since the pump can deliver enough air in real time to operate the tool. The higher your CFM, the less your compressor will run with continuous tool use.
Power
The horsepower, often abbreviated HP, of a compressor is a sometimes misleading figure. Horsepower describes the power output of the motor. The motor must work together with the compressor to actually fill your tank with air. While the horsepower rating on a compressor can give you a rough idea of its output compared to other compressors, we suggest focusing on the CFM rating.
Pumps
Air compressor pumps come in a variety of flavors. Two of the most common types are oil-less and oil-lubed. Oil-less pumps are generally maintenance free but in trade typically have a shorter lifespan. That said, these pumps tend to have a smaller package size and weigh far less than their oil-lubricated counterparts.
On the other hand, oil-lubed compressors require you to maintain oil levels and perform oil changes to keep them in good running order. Oil-lubed pumps tend to last longer when properly maintained. They also tend to run cooler and quieter than the oil-less compressors.
Either of the above types are suitable for a DIY auto mechanic, so weighing the pros and cons of each type is merely a matter of preference.
Other Considerations
There are a few other nice-to-haves when differentiating average air compressors from the best air compressors. Other things to watch out for:
● Make sure the gauges can be easily seen and read. These will provide you quick feedback to help you determine the status of your compressor in real time.
● While you can get by with one hose connection (as most compressors will have), having two can save you a bit of time in swapping tools.
● Everyone always thinks about the air power that a compressor provides, but few people think about moving the device after use. Search for a compressor that has good ergonomics that will allow you to comfortably move the compressor without a ton of muscle strain.
● Cheap compressors often have metal feet. Rubber foot pads will cut down on noise transmission and will also dampen a little bit of vibration.
● Although you can get them separately, some compressors come with accessory kits. These can save you a good bit of coin if they are included with your purchase
Best Air Compressors
For purposes of home mechanic use, we have opted to review a variety of air compressor sizes. As mentioned previously, if you intend to do a lot of paint work or other work that requires continuous tool use for extended periods of time, you might find the compressors at the smaller end of the scale a little small for your liking and you may gravitate toward the higher capacity compressors. However, if you intend to inflate tires and power an impact wrench intermittently, you may find that the best value can be found with a smaller compressor as they make some of the best air compressors for this purpose!
Makita MAC2400 Big Bore 2.5 HP Air Compressor
This compressor is oil lubricated, which means that you will have to monitor your oil level over time. This can be easily accomplished with a site glass that is easily visible. It’s relatively easy to drain the oil on this compressor and add new oil in its place so this shouldn’t be a deal breaker. On the bright side, this compressor has excellent longevity resulting from the oil as well as the fact that it runs at a relatively low RPM. Furthermore, the oil lubricated design tends to manage noise relatively well so this compressor is not going to deafen you the first time you turn it on (but you should wear hearing protection when using any loud tools anyways).
Some other notable features are the gauges are easily visible on the front. Everything is neatly packaged into a roll cage for durability and easy portability. There are also two hose adapters which allows you to run two tools simultaneously. Finally, Makita offers a 1 year warranty so should you experience any issues your compressor will be covered.
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Senco PC1131 2.5 HP Compressor
Relative to the Makita, this pump is more attractively priced at about 100 bucks less. That said, it doesn’t feature quite as many bells and whistles as the Makita. This compressor only has one hose connection and is not quite as ergonomic when it comes to carrying the compressor.
This compressor is oil lubricated, so you will have to occasionally change the oil. As a result, you will also enjoy quiet operation and increased longevity as a result. When it comes to quality, the compressor is nice. In addition, it is backed by a 1 year warranty from Senco, which matches the warranty length for the Makita. Overall it’s a great compressor and we don’t think you can go wrong!
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Dewalt 30 Gallon Portable Air Compressor
The Dewalt 30 gallon flows 5.7 CFM at 90psi. It features a 155 psi max and tank capacity for the single tank design is 30 gallons. This compressor is oil lubricated for longevity which makes sense considering that as compressor size and capacity grows, so does price. As such, oil lubrication helps ensure long life to protect your investment.
When you start getting into compressors in this size range, they also start doubling for general shop use. This compressor runs on 120V power, which is a huge bonus. Another nice feature that allows this compressor to accommodate a shop environment is the ability to be easily converted from the standard 120 volt power to 240 volt power (note: as you get larger in size into the 60 gallon or above range, it becomes harder to find 120 volt compressors due to their increased power demands which precludes many amateur mechanics from being able to use them without the significant expense).
As far as design, the tank sits vertically with the motor on top, so the footprint is relatively small despite the larger capacity. Two tires and a handle allow for easy mobility.
Overall, this compressor will definitely expand your capabilities in the garage beyond impact wrench and tire inflation use. That said, quality is good and makes this one of the best 30 gallon air compressors available but you have to pay to play. This compressor costs about double what the above two compressors cost.
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Conclusion
When searching for the best air compressor for your garage, there are lots of considerations depending on the types of tools that you intend to run. We hope that our guide has pointed you in the right direction to help make your buying decision easier. That said, while these are some of our favorites, we know that there are tons of great air compressors out there. That said, feel free to have a look at some more options by clicking here if none of the above were quite the right fit for you. Happy wrenching!