I use Unioil also (16 months now) and do not experience any black smoke but got curious today on the use of 2T as additive to diesel. Based on the threads I've read below, they say it's applicable to SF3 as well. And lots of testimonials from SFCP members!
Sir Larry, did you try? I noticed in one of the threads you were curious as well.
Anyone here who have tried already?
Here are the discussion threads that I've been back-reading:
SFCP thread
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Tsikot thread
http://tsikot.com/forums/engine-fuel...il-fuel-79879/