My understanding and have seen in practice is that the components of anti freeze (ethylene glycol primarily) will destroy the rod and crankshaft bearings if mixed with the oil in even minute quantities.

The older EMD 567 engines (A and B) used a different sealing method at the bottom of the liners and if a unit was shut down for any length of time and the engine allowed to cool these seals would shrink and allow cooling water into the "basement" or oil pan.

Conversions of the A and B engines to use the improved sealing system are referred to as "BC" engines as they allow a "C" head and liner to be used which eliminates MOST of the leakage problems as has been stated by other posters here. Conversion to a "BC" requires fabrication inside the engine block in the way of water jumpers to connect to the improved heads.

As Dave Buccolo stated, recent devlopments in sealing technology has given additional life to these older units and allowed newer ones to use anti freeze.

There is a firm that manufactures special anti freeze for locomotive and marine engines that uses alcohol as the medium and does not damage the bearings, but it is quite expensive and in the case of an older A or B engine that leaks still ends up in the oil eventually.

A lot can be said for the use of the multiple smaller diesels used in the "genset" units so far as freeze protection is concerned; however, I still question the economy maintenence-wise of maintaining 18 to 24 small bore cylinder assemblies thrashing around at a higher speed than 12 to 16 EMD 645 cylinders just "loping" along.