Sorry to post on an old thread but I'm from VMAC and want to clarify a few things, since these posts tend to stick around and other people might use some incorrect info from this post and accidentally void their warranty.
Please note that 100 or 150 weight oil shouldn't ever be used with VMAC air compressor systems, as it can cause problems with the system and will void your warranty.
In addition, VMAC cannot recommend alternate compressor oils. VMAC compressor oil is a synthetic lubricant specially formulated with an additive package for our rotary screw compressor that allows it work at the high rotor speeds, high air pressures, and higher temperatures our compressors run at. This lubricant also works properly in our Air/Oil Separation process.
Poor performance of, or failure of a VMAC system resulting from the use of non-VMAC compressor oil is not covered by VMAC Warranty.