DEF fluid in heavy equipment !!

[Mikem]

From a non 1-1 truck guy only 1/14 what is DEF fluid supposed to do , nobody here can seem to tell just u are to use it . Li'l giants my friend in town who has about 40 heavy equipment trucks keeps buying used engines and sending them out to be rebuilt . He has also complained about the price of used equipment . He also told me that the 4 companies making DEF are all owned by one senator in the U.S. . MIKE