Its 30-50 cents cheaper because the producer probably isn't paying road taxes (hence the tractors pulling in). He also is making bio out of at least some WVO instead of raw soy or canola stock. That keeps costs lower.

If you are interested, Id ask him for a copy of ASTM test results. This tells you most notably if the fuel is 'dry' enough (water eliminated correctly), amongst other fuel quality parameters. There are ways to test bio at home, but usually a retail outlet has the results from a lab on hand.

Biodiesel from soy WVO should look straw colored and flow almost exactly like D2.

Your exhaust should smell like you heated a pan on the stove, and threw new vegetable oil on it. My bio comes from tortilla chip oil, and I never pick up the food-that-was-cooked-in-it scent in the finished bio or in the exhaust.

By the way, going from B100 to D2 will make you wonder what is wrong with your engine, the noise increase is more noticeable going back.

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car