Quote:
Originally Posted by UFO
Here is my understanding of the ULSD reformulation. The sulfur is not a lubricant, however the process of removing the sulfur also reduces the fuel lubricity. In addition to the ridiculously low cetane of the new ULSD fuel, and what I perceive to be less energy, I never run straight D2. Even during winter I run at least B20. I get better mileage on biodiesel than pump diesel; this I have tested back-back directly, it's less than 5% difference, but that's why I think there may be less energy in the ULSD -- might be cetane differences too, but since we are in the Unicorn Corral we are allowed to speculate rampantly.
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From what I understand biodiesel contains less energy per gallon than D2 but it burns more efficiently. So (and this is only based on what I've observed myself or read on other forums) in concentrations below B50 the more efficient burn of Bio allows a more complete burn of the dino-diesel, thus raising mpgs a bit. I've noticed a difference on my car but never my truck. Bio also has significantly better lubricity (#1 on the study) so whenever I can run it I don't run 2-stroke.
Interestingly Biodiesel also acts as a fuel system cleaner. Guys on the TDI forums have said that running one tank of B100 loosened enough gunk to completely clog their fuel filter.