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I've never owned an engine-driven compressor but if you are looking for something portable that can be used where there is no electic power available, then you are pretty much left with that for a choice. I agree with CN, the number that is most important is the 13.5. I disagree with the reference to SCFM (Standard Cubic Feet per Minute) but that seems to be common practice among some manufacturers. I'll blame it on ignorance of marketing departments. Compressors should never be rated in terms of SCFM because the rating would then vary, depending on the location of the compressor. Compressors are more properly rated on inlet CFM (ICFM), sometimes also referred to as "free air CFM" or just plain CFM, interpreted to mean CFM of ambient air. That way, the rating is independent of location. ICFM is the about the same, numerically, as SCFM only when at sea level and "normal" ambient temperatures. If you happen to be located in Denver, CO, for example, any true SCFM rating would have to be discounted by about 20% to get a meaningful air rate at that lower ambient air density. In any event, I'll take the 13.5 to really mean inlet CFM of ambient air and not really SCFM. The other point that CN makes is that there is no reference pressure point for the CFM rating, e.g. 100 psig. My two stage is rated at 175psig and the CFM rate is stated to be at that pressure, not the more common ratings such as xx cfm@90 psig, yy cfm@40psig that you usually see attached to single stage machines. The one you are considering is indicated to be a two stage unit. That's good because you'll get cooler air out of it than a single stage one. That is, if you can call 300 or so degrees F as being cooler :o). In any event, moisture control is easier with two stage units because of lower discharge temperatures for the same discharge pressure. I know it's risky to assume but I'll assume that the 13.5 cfm is taken to mean at 175 psig, similar to my compressor, since it is not stated otherwise. That would mean you'd probably get 14 or 14.5 cfm at the common 90 or 100 psig reference point. Even if that assumption is wrong, the 13.5 should be satisfactory for your intended uses, if it's at any reasonable pressure point. I consider any CFM rating at 40 psig to be essentially meaningless. You aren't going to do much with a tank pressure that low except dust removal with a blow gun. I think you'd be very satisfied with that compressor. At least from what I can see of the specs. It should do about anything you want except extensive sandblasting. While most sanders and grinders will require more than the 13.5 on a rated, continuous basis, most people do not run such tools at the full throttle pressure (usually 90 psig), do not run them at full rated speed and do not run them continuously for long periods. Although I wouldn't recommend it to others, I made do for many years with only 6.8 cfm@90psig (20 gal tank) using all kinds of tools, including spray guns. So unless you are in a production situation, I think you will do fine with 13.5. About the only probable situation that I can think of, except sandblasting, where you might have to wait every once in a while for the pressure to regain itself is in using a DA sander. The 30 gal tank is a little on the small side but is a necessary compromise to keep the unit reasonably portable. I would like to see a little slower pump rpm and a Honda rather than a B&S engine, but hey, you can't have everything and that price is pretty good for what you are getting. Just remember that the engine will run all the time you are using the compressor, even if you are not using air. It makes no sense to shut things down if you are going to use it again in a few minutes. The engine simply unloads and idles automatically when the tank pressure gets up to the cut-off point (175 psig) and automatically loads and throttles-up when the pressure drops to the cut-in point, likely 145 psig. You'll have to shut the engine down manually when you are really done using it for that session. All engine-driven compressors are like that so it's not specific to this machine. Go for it. It seems to meet your particular needs nicely.  Rod
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