Less BTU means lower fuel economy. "If you get to B100, you suffer a 5% to 8% energy loss in the fuel," says Hall. "That is physics. There is nothing we can do about that."

However, the power loss becomes negligible at lower blend levels. "If you go down to that B2 to B5 range, the chances are you are not going to be able to see any noticeable difference in power," Hall states. For example, if B100 were 7% less efficient, and B5 contains only 5% biodiesel, the total difference in fuel economy would be only .35%.

"When you look at the amount of fuel that gets consumed on jobsites, if I were to switch to a B100 and see a 7% or 8% BTU difference, I think I would be scratching my head a little," says Borgman. "But in those lower blend ranges of B2 or B5, I would recommend that everyone use them."

Cold weather capability
Another common concern with biodiesel is its cold temperature performance. Yet, this is a concern with No. 2 diesel fuel in general.

"Biodiesel will gel in cold temperatures, as will No. 2 diesel," says Pearson. "Up to B20 can be used year round in all types of climates if it is properly treated," says Pearson. "B20 is handled in a similar fashion to No. 2 diesel - treated with additives or by blending with No. 1 diesel for year-round operability."

The percentage of biodiesel in the blend determines how the fuel will react. "Getting up to 20% or 50%, it is going to be a little easier to notice the differences," says Borgman. But blends at lower concentrations, such as 2% to 5%, are not as much of a problem. "If you have in-spec B2 and B5 blends, then any of the normal additives you would use for cold flow improvement are going to work for you, and you should not see a difference."

However, not everyone is ready to recommend biodiesel blends for use in cold climates. Given the recent switch to ultra-low-sulfur diesel fuel (ULSD) for the on-highway market, Stearns advises a more cautious approach. "I recommend you try to limit biodiesel use in colder climates. That just throws another variable in, especially right now with the transition to ULSD," he states. "ULSD has a higher cloud point and needs more additization. [It requires] blending with ULS kerosene or with No. 1 diesel - which are not very available at the moment. Then you throw biodiesel on top of it, which has a much higher cloud point itself."

Concerns about cleansing
Equipment age also has a lot to do with biodiesel compatibility. "B100, as well as blends of increasing biodiesel content, can act as a cleansing agent to rubber components on engines older than 1994, breaking them down over time," says Pearson.

Hall agrees, adding, "The solvent nature of biofuels is definitely going to have a higher impact on some of the older materials we used to use." This is less of an issue with more current machines. "We started using more plastic types of seals in the late 1980s and early 1990s, moving away from natural rubber in a lot of our applications."

In 1993 to 1994, seal materials switched from rubber to current materials in response to lower sulfur diesel fuels, Stearns explains. "Since 2000, all of the Caterpillar product has been using Viton seals," he notes. This eliminates compatibility concerns. "As people are switching over older engines, they should watch for seal leakage or degradation."

"We suggest changing out those parts with synthetic products instead," says Pearson. "You would not need to take those precautions with a B5 blend, however."

Equipment fuel and storage tanks can also present a challenge. "Blends of biodiesel can act as a cleansing agent on sediment in the fuel system from previous regular diesel use," says Pearson. "The higher percentage of biodiesel in the blend, the higher the cleansing agent to the fuel. We recommend keeping an eye on fuel filters for the first six months of use with biodiesel blends."

The biodiesel will eventually clean up the entire fuel system. "It will dissolve anything that has been deposited, whether it is in the fuel storage tank or the fuel tank itself," says Stearns. Unfortunately, until the system is completely cleaned, the filters protecting the fuel injection pumps and injectors may plug prematurely.