I would not use any oil where the oil manufacturer specifically states that the oil should not be used for breathing air applications. In particular diesel motor oils are full of additives which are designed to protect the longevity of the oil in "internal combustion engines". Many of these additives have high respiratory toxicity and should not be used in a breathing air compressors not to mention the mineral base oils often have high concentrations of narcotic aromatics such as ethyl benzene, xylene, and toluene.
Oils specifically chosen for breathing air applications have lower concentrations of aromatics and fewer additives resulting in fewer gaseous vapors sitting above the oil which must be removed by the activated charcoal.
All the diesel motor oils contain an anti-wear additive known as ZDDP which under the right compressor conditions can produce hydrogen sulfide which is not removed by the standard charcoal found in most purifiers.
If you really must use a mineral oil in the compressor I'd have a look at Shell Corena P150 mineral which Bauer USA rebrands as oil #26. It has been approved by Bauer and while it has some toxicology issues the oil certainly is better than a diesel motor oil.
