Originally Posted by
Dave Mayer
Very good... soaps are molecules in which one end is polar, and the other non-polar. The non-polar end attaches to the oil or grease, and aggregates into little bubbles of hydrocarbons dispersed in the water. I haven't checked the solubility charts of oils mixed in water with detergents/soaps, but I can tell you from hands-on experience that mineral spirits is far more quick at degreasing than any any water/soap/detergent mix I've ever used.
However,, when degreasing with soap/water, you are left with a mix of water and hydrocarbons which goes where? Water evaporates at a far slower rate than mineral spirits, so you are left with a large volume of liquid mess that just begs you to be flushed into the sewer system.
Second, the 'green' degreasers are not as much soap based, but depend on strong acids for degreasing. You do not leave metal parts in these for any length of time. In contrast, you can leave metal bike bits in a hydrocarbon-based bath such as mineral spirits. I have: chains a derailleur bits left forgotten for months with no apparent effect.
Plenty of companies out there that can recycle/properly dispose of dirty mineral spirits or dirty aqueous-based cleaners for you if you're a commercial business, and local household hazardous waste drop off facilities can take them from a homeowner (at least in my area). Most of the general purpose cleaners I've dealt with are not acids, but either alkaline or some other type of material (I can't remember the general group name) that'll easily remove most any oil or grease (sometimes it takes a little scrubbing).