Here is a link to a blog post of mine containing some pics of the UP 3985 on the day I *finally* caught a UP steam train operating on former CNW (and RI/MILW) tracks (i.e. the "spine line" in Rosemount, MN):

http://www.tonyheld.hoboandbowser.net/up-steam-at-last/

Can anybody tell me why the 3985's exhaust is so clear and clean? That surprised me when I saw it.

That is probably the result of a very experienced crew that knows their business.

Mixing diesel with the fuel would probably make more smoke, not less, since you'd have to overfire to compensate for the lower BTU content of diesel vs. the normal, heavy oil.

Thanks for the feedback, lincoln. I never knew that.