In my opinion one of the most important things about your compressor is to use the right oil and change it periodically – that will ensure a long life for the compressor. Especially if you built it yourselves following my article about Homemade Compressor. If you have bought a professional one you will find the relevant information in the manual.
Talking about the homemade compressor we don’t have to speculate that much as nobody’s compressor has broken by the choice of oil yet it might cause issues with overheating and therefore impact the amount of time you spent airbrushing. So the question is “Which oil to use?”. Here’s what I’m going to recommend.
My point of view…
Factory that makes those compressors fills them up with mineral oil and freon (cfc – chlorofluorocarbon) or some people call it compressor oil. Doesn’t matter how we’re going to call it, to be exact it is an mineral oil. This means that this oil does not have any additional chemical ingredients except freon as gas which will evaporate as soon as you open the compressor.
That is ok as far as it is used in closed environment (no air) so there is no external factors that might impact it’s characteristic. But we’re going to use it for our purpose – airbrush, where the situation is significantly different. The environment is not closed anymore – it is opened, full of oxygen, dust, humidity … etc.
Update from wikipedia
CFCs and HCFCs are colourless, volatile, toxic liquids and gases with a faintly sweet ethereal odour. Overexposure at concentrations of 11% or more may cause dizziness, loss of concentration, central nervous system depression and/or cardiac arrhythmia. Vapors displace air and can cause asphyxiation in confined spaces. Although non-flammable, their combustion products include hydrofluoric acid, and related compounds.
Mineral oil in these conditions is loosing its properties really fast. That causes compressor to overheat, raises noise level, and causes damage up to point where the compressor is broken … even with the right amount of oil. Not mentioning that air that we use for airbrush will be full of oil vapours :(
Motor oil compared to mineral oil is solving these issues as it has bunch of additional ingredients that will compensate or even remove all factors that affect the quality and life of the oil. Motor oil is made to be used in more aggressive environment as in airbrush compressor so it can last much longer. Good motor oil has more classifications, for example I use semi-synthetic 10W40 as I have some left after I changed oil in my car. You can use mineral or semi-synthetic oil with different indexes but I wouldn’t recommend to use synthetic oil (it is more expensive and it is thin -> short life)
I think that’s enough of facts. Now I would like to see your opinion.