Originally Posted by
Piedmonster
Type III is occasionally found at some southern outstations who want tDI fluid on hand for the rare occasion needed, where the station is mostly served by Turboprops. Type III has a lower sheer speed designed for DI/AI use on aircraft with "slower" rotation speeds.
Again, it's very uncommon, but it is used in the US.
Type II is actually banned by the EPA now (at least according to the instructor in my RGS) and Type III is extremely common for turboprops. All the Colgan outstations use it. You'll never see it used on a Jet though (at least you shouldn't).