I have a 20 Gal 4 HP Campbell Hausfeld. It`s good for blowing up baloons and checking tire pressure.
Can`t really run any air tools with it, it runs out of oomph, take too long to catch up. I was using my paint sprayer and it couldn`t keep up.
problem with a too small compressor, is it constantly runs and you have hot air, then the air cools in the hoses and moisture condenses in the lines.
with a larger unit, they don`t run as much, and the air has some time to cool, which lets some of the moisture to drop out in the tank.
you do need to have good air filters and moisture traps.
The oil less units are really noisy compared to the oiled compressors.
two stage are more efficient than single stage compressors. 2 stage usually pump up to 175# compared to single stage 125#.
2 stage cost quite a bit more.
If you decide to buy a used one, check for rust in the tank, I bought an old used one 15 yrs ago, had a 60 or 80 gal tank, 5 horse honda gas eng. and huge 2 lunger compressor. that thing could really pump some air. the problem with it, the whole thing was cobbled together. I used it mostly for body work, painting etc... had to leave the bleed open to keep pressure where I wanted it, and it didn`t have any way to idle the engine when it reached pressure.
I opened the large plug on the end of the tank to take a peek in side ( do this when the air is depressurized
) and was surprised to the amound of rust inside, thick blistery. date on info plate was dated 1946. so I sold it as soon as I could
.
then I went too small compressor
Charlie