CFM displaced is the amount of air the pump draws in and compresses. Free air delivery is what actually reaches your equipment. The displaced number is always larger, and some manufacturers lead with it in their specs because it looks more impressive on paper. The number you want is free air delivery. That's what you'll actually have access to on the job. If a spec sheet only shows displaced CFM, ask for the delivered number before you commit to anything.
Start with your CFM requirements. The pump needs to deliver at least as much air as your application demands. If you're replacing a pump on an existing compressor, match or exceed the output of the original. Not sure where to start? Give us a call and we'll help you work through it.
The main thing is the oil. You need the correct type for your pump, the right fill level, and regular checks to make sure it stays there. Too little and the internal components won't stay lubricated. We provide oil recommendations for all of our pumps and train our distributors to walk customers through exactly what each model needs. If you're not sure what your pump requires, contact us before you guess.
Oil lubrication in a pump works by splash. As the internal components move, they throw oil around the crankcase to coat everything that needs it. If the pump isn't sitting level, that oil can't distribute evenly and you'll get wear in areas that aren't getting lubricated. This applies whether the pump is on a portable compressor or mounted in a larger piece of equipment. Check the level before you run it.
