Found a truckstop that is selling Bio. Have ran two tanks and notice about a 2 mpg decrease in mileage. It does run and idle alot better, and when the go pedale is put down hard not as much smoke. Is this drop in mpg normal for a bio blend? I'm thinking also that the dino in the blend may be a winter blend. Its funny both the bio and dino that i am using comes from the same supplier, but they only offer the bio at the truckstop, International service center.
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Randy B's Sig:

Buddy all dressed up and no where to go!

I always get better mileage with B20.More Cetane,and makes fuel slippery.But so far thats a 3. litre engine I.D.I.

oldsinner111's Sig:

OM617.951 the last of the bullet proof diesels.

I've found that my mileage is slightly lower when using bio, but the benefits outweigh the slight loss in mileage, especially if you're making your own.
This is from 5 years experience with the stuff, testing from b100 down to b5 or so.

DeLuzGN's Sig:

1999 Dodge Cummins, Q/C, 4x4, auto w/ some upgrades (previous owner did something to the trans....), FASS hpfp w/ 1/2" lines, Isspro EV fuel, pyro, boost, trans temp, Smarty, power puck, AEM Brute Force intake with Amsoil nano-fiber filter, silencer ring MIA, straight pipe, corroded black paint, homebrew biodiesel.

Bio has aobut 10% lower BTUs (energy content) than petro diesel, but about 20% higher cetane value (55 vs 45). The lower BTUs tends to cause mileage to decrease, but the higher cetane value results in a slower more complete and efficient burn.

From what I've read, the net effect is usually a very slight drop in mileage, but if the engine is tuned to compensate (by advancing the timing a degree or so) most people find that its pretty much a wash. I've found that to be the case with running B20 in my Mercedes and my F250 - which are both IDI engines.

As I understand it, the higher cetane value is why the engine runs quieter. Although it shortens the time between injection and the start of ignition - allowing more time for the fuel to burn - at the same time it decreases pre-ignition - which reduces the "rattling" sound that is similar to "pinging" in gassers. Advancing the timing a degree or two will make it sound more like its running dino, and boost both power and mileage a tad. Another way of looking at it is the low cetane of regular diesel forces you to detune and retard the timing more to supress pre-ignition rattle.