Originally Posted by cyccommute

Simple Green is slightly alkaline and can lead to some reactions with metals that result in cracking. The Klean-Strip® Green™ Odorless Mineral Spirits you linked to isn't 'mineral spirits' in the traditional sense. It's about 40% light end petroleum distillate and is an emulsion. If you are emulsifying petroleum, you are probably emulsifying it with a water based material or some other polar liquid. The MSDS says that the liquid melts at 0 C and boils at around 100 C. Suspiciously, that corresponds to the properties of water and I suspect that they use a surfactant to get the petroleum distillate into an emulsion. That makes the 'mineral spirits' far more like Simple Green than petroleum based mineral spirits.

Real mineral spirits should be a colorless liquid with a slight to strong petroleum odor. It won't damage parts because it can interact with the parts. It will dissolve grease but you could soak your parts in it for decades and never have any kind of corrosion or damage...to metal parts. Plastics bits are different.

Your cracking issue is with the green part of Klean-Strip® Green™ Odorless Mineral Spirits. Because they added a polar liquid (likely water), soaking parts in that mixture isn't benign.