Which Is The Best Air Compressor to Get?
 

My 25-year-old Sears 2hp with oil-lubricated compressor and 25-gal tank finally died. It was dying for a while but I wasn't listening.

On Memorial Day weekend I went to Harbor Freight. They had a 30gal/2hp/oil-lubricated model for $360. Not subject to any coupons. They were out of stock. Otherwise, it would have stopped there.

But then I started looking. My first surprise was at Home Depot. They had two ~1.8hp oil-free models, one 20gal for $200, one 30gal for $300 that went to 175psi, pressures usually in 2-stage, 240V shop models with 60gal or 80gal tanks.

Looking further, there is also a DeWalt with a 27gal tank that goes to 200psi for $500 and an Industrial Air with a 15gal tank for $380 that goes 225psi. And a few others that looked similar with different labels that looked similar, but those three (Husky, DeWalt, Industrial AIr) had the best specs. It turns out they are made by the same firm. Each client changes the plastic cover, color, and label. picks different tank sizes. Industrial Air is their own label. These have a 50% duty cycle, so not something for a production shop. But I work on cars and lawn equipment.

The advantage of high pressure is in this video. In addition, especially with a large tank, lets the user do tasks (e.g. media blasting) that a typically are way past the capabilities of an oil-free design.


Then came two more. There is a popular air compressor oil-less compressor model currently being widely used that has an electric motor between two single cylinder computers. It looks nice. It is usually packaged as a low noise option; the two cylinders provide a decent volume of air at low speeds, about 1700rpm. That is very important for contractors who work indoors (e.g. finish carpentry) but only have 125psi or 135psi tank pressure, and typically with smaller 10gal or 20gal tanks.

However, California Air did a version where they connected the output of the first cylinder to the input of the second. A 2-stage 175psi oil-less compressor for $440. This is a picture of its motor/compressor, you can see one cylinder has an air filter and the other has an input tube with cooling fins wrapped around it.

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Googling around trying to find reviews and relative analyses, I came upon another, talked about as a future on the Campbell-Hausfeld Facebook page and with a listing on their site, no price, no retailers. Further investigation reveals it has been at Lowes as an exclusive private label for a year at $500. What makes this one unique it is a 30-gal, 175psi, 2-stage oil-lubricated with a 2hp 110v electric motor. I think it may be the only one with that spec. 175psi is a popular max setting for the 60gal-80gal 240v compressors. It has a higher duty cycle (70% vs 50%) and higher life span than the oil-less models.

Does anyone have experience with these? A better understanding of the advantages of tank pressure vs. tank size? Of oil-less vs oil lubricated compressors? Of two-stage vs one-stage compressors at the same pressures? Of the relative importance of cut-in vs. cut-out pressures?

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It has been a while since I paid much attention to air-compressors, but in the past the less expensive oil free direct drive air compressors generally made quite a racket. A lot noisier than an oil-lubricated belt drive unit. That might have changed with time, or when you get into higher price brackets. In addition to max PSI, you'll want to know what the SCFM requirements are for any air-tools that you plan to use in the future to see if the air-compressor you're shopping can deliver enough air flow for what you are wanting to do. When comparing CFM ratings of various air-compressors check to see were conducted at the same PSI (I think 90psi is pretty standard).

The manufacturer's rate all these units at 5.1-to-5.4 CFM@90psi except the California Air which is 3.8 CFM. The same compressor/motor run in tandem instead of two-stage is also 5.1.

The CFM counts, but all 120V compressors are limited by the power from the wall. What we are really working off is the compressed air stored in the tank. Contractors who don't need the volume use compressors with small tanks, typically around 4 gallons.

I did a little model compare the relative mass of air (which is a function of volume and pressure) at cut-out and cut-in, and then applied different drawdown rates using the tank only above cut-in, then subtracting the compressor's output below the drawdown. As you might expect, the bigger, higher pressure tanks store the most air with the 27gal@200psi DeWalt on top by a bit. The greater the air requirement is compared to the compressor output, the more the amount of stored air becomes more important. As the compressor output comes into play, the cut-in pressure (when the compressor turns on) and its output volume count. Then the Campbell-Hausfeld/Kobalt scores narrowly over the DeWalt. The Husky 30gal@175psi loses to the Kobalt because of lower cut-in pressure (135psi vs 145psi) and lower compressor CFM (5.1 vs 5.4 CFM@90psi). Note that the Industrial Air video compared 15gal and 20gal tanks.

There are some things that just work better with more pressure. This includes blowing a tubeless tire on to its rim and inflating tires in general. The big flow items are media blasters and spray guns. The oil-free compressors have aluminum cylinders which have a much lower service life. The oil-lubricated Campbell has cast iron cylinders with aluminum heads; I'm told but not sure that gives it 3x-4x the life expectancy. They all would probably work. The life expectancy may or may not be a problem (my last compressor, with cast iron cylinders, outlasted by the previous oil-free by a lot, <10 vs. >20.

Warranties also vary. Some are 1 year, some 2, some 3. The extent of what they cover also varies but in all cases I think the service will be ok.

My wife would like me to get the least expensive, the $300 30gal@175psi/135psi oil-free Husky. With all between $300 and $500, features could be worth the difference, with the $500 DeWalt 27gal@200psi/160psi oil-free and $500 30gal@175psi/145psi oil-lubricated Kobalt on top. But I don't really know, therefore this post.

Interestingly informative answer in the Lowes Q&A on the Campbell Hausfield/Kobalt compressor:


"Is it better to run synthetic oil in this unit ??"
Anonymous on 11/19/2018
1 Answer


https://photos-us.bazaarvoice.com/ph...9-d6aed87a95a2
Kobalt Team on 11/20/2018
It is fine to run either synthetic or mineral based 30W non-detergent compressor oil in any of the Lowes Kobalt 2-stage cast iron air compressors because the 2-stage pumps run so cool. The advantage of synthetic oil for a 2-stage product is that it increases the time between oil changes. For single stage units synthetic oil is better because it has a higher flash point and since single stage units run hotter they need synthetic oil to avoid carbon deposits left by mineral oil.

I 've used a Makita 2HP compressor for the last 9 years. I filled the oil reservoir with Mobil One, 5W-30 (same oil that I use in my S2000). This has been a very reliable compressor. Starts every time, quiet running. :)

What tools do you use with that? It seems to be rated for a fairly low airflow (3.3 SCFM@90 psi) and it has a very small tank, 4 gal. The pictures and videos show it being used by carpenters to drive nail guns; none show a mechanic with any typical automotive application (e.g. impact gun, shear, riveter, grease gun, media blaster, etc.).

Air compressor tools are going the way of tapes, CDs, and Apple Music.
Electric is replacing everything as they can do everything and more. Don't replace it with another, get rid of it once and for all. Use what you save to buy some decent replacement tools. EBay the old air tools.

I sold all my pneumatic tools, except for my air chisel.

Generally, the new electrics are cordless and cost 2x-4x as much as their pneumatic equivalents. The electrics are also much heavier. Please show me the electric plasma cutter and media blaster. Or tire inflator, tire mounter (where you blow the tire against the bead), pre-oiler, and oil extractor. My angle grinders are corded electric, and I have both corded and battery-powered electric drills. I generally reach for the corded tool then, it always seems less aggravation for more power than battery-powered.

Then there are the pneumatic nailguns, but I do have a small pancake for that. Its small tank can't handle the automotive tools though. It has been getting me by before I get the new unit, barely.

Electrics are very popular for autocross, drag race, and track days where entrants drive the race car to the track. They are also popular with home repair folks where running electric cords or air hoses is problematic.

Air chisel, angle die grinder. No electric equivalents yet, cordless or corded.