Used to work for an ag operator who had a contractor running his Airtractor with a PT6-34AG on diesel. The first time I started it, it scared the hell out of and the rest of the airport. The smoke during light off was incredible.
Can't recall the exact figures but know it took a couple of hundred Hrs off the TBO and HSI's.
There is S.G. adjustment on top of the FCU to cater for diff fuels. Never have that aircraft long enough to see what the HSI was like and never heard.