I looked at a lot of different comments on the web about people's experience with diesel vs. kerosene vs. Klean Heat in the small heaters. I've burned all three over the years in much bigger stoves on larger boats and in a yurt that I still have. Diesel is cheap (relatively), burns hot, smells, and can put out an enormous amount of soot under some conditions. Soot is the biggest problem in stagnant air conditions. I don't know yet whether my D2, with forced air into the burn chamber, will produce soot. But on a boat when a little piece of soot lands on the deck it turns into a greasy black streak that can only be washed off with soapy water.
I used to burn Pearl Oil (Standard Oil's double refined K-1 kerosene) because it was available at the Ballard fuel dock and, at the time, was only slightly more expensive than diesel (85 cents a gallon). I could also use it for my kerosene lamps (no house battery on a live aboard!). It burned clean enough to not put out soot, but when prices went up I removed the stove's day tank and took diesel directly from the main tanks.
A friend gave me some Klean Heat when I first put a Dickenson diesel stove in my yurt. I had been burning Pearl Oil and 5 gallon buckets of kerosene from the hardware store (then $16 a bucket). We could see the stove's little glass window into the burn chamber when in bed, so we knew what the flame looked like when we idled down for the evening. Klean Heat was amazing. Unlike the yellow flame from diesel, Klean Heat idled down to a tiny wisp of blue. No soot, no smell, but when I found out that it was $5 a gallon, I never bought any (until recently).
What I found on the web was a thread where people were talking about burning diesel as their regular fuel and then a once-a-year "cleaning" with Klean Heat. A lot of heat and not much light (I mean the discussions). Then somebody opened their diesel-fired heater and took a photo of the carbon build up. Put their heater back together, ran Klean Heat at full bore for 45 minutes, reopened the heater, and took a picture. There was a clear improvement. In fact, the burn chamber was clean. Question is, could running the heater on diesel for 45 minutes at full bore do the same thing?
Anyway, I just bought some Klean Heat for my Espar D2 because the initial testing was inside my shop. I didn't want smell or soot. The test run produced exhaust that was basically warm, moist air with a faint hint of petrochemical smell that went away quickly (because of my exhaust fan). But with tax, Klean Heat is $11 a gallon, so I'll probably run diesel and just use it as an occasional cleaning tonic.
Mark