That's too bad about Solar Market. I went there from RI starting in 2003 when I got my first diesel. Nice folks there. Anyway, I would fill my car plus some 5 gallon cans, and take about a month between fuel runs. I still do that in the winter, running up to Acton, Mass, since the locals don't sell B100. You may have to go to Rymes near Nashua, NH if you want B100. I suggest 8 cans in the back of the car. That may last you a while, depending on your commute. Don't tell your homeowners insurance company, they think this stuff is flammable.
http://www.biodiesel.org/buyingbiodiesel/retailfuelingsites/showstate.asp?st=NH
Bill
PS Didn't there used to be a co-op near UNH? Oyster River, IIRC. I don't think they have a pump.
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