I'm getting ready to buy a new air compressor. I have a choice between a 25 gallon, 6HP direct drive, oil free model and a 25 gal., 6HP oil lubricated model. Same manufacturer, same 135 psi max., same CFM rating. The oil lubed model costs $35 more. So guys, what's the pros and cons of oil-lubed vs. oil-free air compressors?
6 horsepower is a large compresson, is it for other than home use? Oil bath compressors last a very long time, oil free gives cleaner air such as used in auto painting or craft services. What is your application?
Thanks for the response, Mitch. Actually the two compressors that I am comparing have 2HP motors that can develop 6 peak HP (advertising gimmick) I will be using it for keeping air in tires, running air wrenches and other tools, cleaning auto parts, etc. I doubt if I'll ever use it for painting.
oil filled have advantages, they run slower/quieter, last longer. the oiless are louder, run faster, make more heat. my small airless one stopeed pumping air because the rubber ring seal on the piston wore... marvel mystery oil , it pumps fine. if your running light stuff, every now and then, the cheap airless one is oky if your going to use it daily and heavy, a cast iron oiled filled one is better. 9 times out of 10 the thing that goes bad is the pressure switch, the fittings and the electric motor. the pump itself rarely fails.
May I suggest use oil-filled... we have much less problems with them at work... run quieter, cooler, and last forever... you can always purchase an oil seperator filter if you are doing any type of painting... Dave
You got the answer on the lubed versus non lubed. You did not asked about a direct drive versus a belt drive but let me advise you. Air compressor manufacturers compete in a world where honesty does not rise to the top of the heap. I worked for a major manufacturer for 12+ years as an engineer. Here is a synopsis, direct drive units have bearing failures as the crankshaft beats hell out of the motor bearings. All small compressor manufactures lie about the compressors indirectly. They advertise their units by horsepower. Any decent compressor can make 4 CFM per HP. When you find the small print as to the CFM and divide it by 4 you find that these small units will require about half the horsepower that is mounted on the machine. These motors are typically identified with the letters SP at the end of the frame design. That means "special". These dedicated motors can deliver the labeled HP for some short duration but these motors are not required to delivery the HP advertised on the sales literature since the compressor they are driving is undersized. Buy a belt drive and get the most CFM per dollar that you can find after determining the amount of air you will be needing for the tasks you will be performing. Run synthetic oil in the compressor. This will give long life to the compressor as it will avoid the valves from carboning. Realize that a piston air compressor has a duty cycle (typically 80 % loaded) and is not intended for continuous loaded operation and factor that into the CFM required.
For one that will be used all over go with the oil less. Mines probably 20 and still going strong.No oil to leak out or run low and forget to check. mikell
I'd go with the oil lubricated one. Call me old fashioned but I much prefer the design philosophy of years ago---slow rpms, long stroke=long life. These days most of what you get as a consumer grade compressor wind up fast and spin like crazy and don't last nearly as long as the older styly ones.
I bought an oil-less portable direct driveand while it works just fine the noise drives me nutz. It is cleaner than my shop compressor and I have used it for painting though it has a tough time keeping up with air tools.
agmantoo is absolutely correct on the horsepower thing, which is nothing but a marketing lie. Figure it out: One horsepower equals 746 watts. So a true 5 HP motor would consume 3,730 watts. Most of these compressor motors run off 110-120 volts from receptacles and wiring rated at 15 amps (1,800 watts) If they were producing a true 5 HP they'd be popping the breaker constantly. So they're not and hence the marketing lie. And the bigger the tank the better -- less time between motor startups. In my opinion, anyone who isn't in the body shop business and just needs a utility compressor around the place is wasting money on a big, expensive unit. I have a no-oil Campbell-Hausfeld 120v, "5 HP" compressor with 125 maximum psi, 5.1 SCFM at 90 psi from a 13-gal tank. It cost $199.95 at Wally World and will run a framing nailer or any similar air tool all day long. My son-in-law paid $50 more for a Porter-Cable with a 3-gal tank that's basically useless. Do I expect my cheapie to last forever? Nope -- but it might. I've had it three years, use it practically every day for something and it's still going strong with no signs of faltering. Noise? Get a pair of earmuffs -- or stay away from machinery.
