Harsh northern climes can turn biodiesel -- a fuel made out of vegetable or animal oil -- into a mayonnaise-like goo. To avoid cloudy fuel tanks and clogged fuel filters, many biodiesel makers and distributors recommend blending biodiesel and petroleum diesel in winter.

But the most recent Northwest cold snap didn't seem to have much gelling effect on local biodiesel users running on B99, a 99% biodiesel blend, according to Propel Biofuels founder Rob Elam.

"A number of customers contacted us to tell us how they expected to have some trouble and they didn't," he said.

The B99 biodiesel blend distributed by Propel (and manufactured by Imperium Renewables) is made out of canola, and is "good down to 9 degrees Fahrenheit," Elam says.