Gaseous
That's very helpful. Since my first sample was unfiltered, bottom of bowser stationary for 5 months, then placed open in high heat/sunlight, I got similiar but a bit more dramatic results. I ran a sample through from the nozzle (which is filtered) and got similar results to you in slightly cooler conditions and less sun. I think the heat/sunlight/evaporation is the reason, not likely microbial (more typical of Jet A and quite fragrant).
I've ran my weed trimmer, mower, and gas blower on the samples and did not have to autorotate any of them. However, I'm ordering a field test kit for water and microbials before I fly the fuel. I'm feeling much more optimistic that it will check out.
Thanks for all the input. Here are a couple more relevant websites I found along the way:
http://www.globalsecurity.org/milita...-1/CHAP13.HTML
http://www.faa.gov/fsdo/orl/files/advcir/AC20-43C.TXT