B20 would be inconsequential, however the difference in viscosities between petrodiesel and WVO can cause stratification between the two if left to sit. While Biodiesel and petrodiesel are similar enough to not cause problems. This also brings up the matter of nozzle spray patterns under different fuel viscosities and unburnt fuel. I noticed you said it ran fine all summer. A simple inline heater and an extra heated filter would help tremendously.

__________________
Jeff
AKA: "El Jefe de Biosmell", at your service.
Locally brewed B100 100% of the time.

83 300TBD-T 300,000+/3+years B100
82 Datsun 720 Longbed 86,000/B100
81 300D AKA: The Turd/parts(gone to the bone yard)
75 O309D AKA:The Blue Turtle/76,000

83 VW Golf Diesel/ Girlfriend's
83 F250/ Girlfriend's
Sold all the gas burners!