Some research I did a few years ago on this subject.
Posted March 10, 2016
1. From U. S. Department of Energy: Alternative Fuels Data Center: http://www.afdc.energy.gov/fuels/biodiesel_blends.html
"Pure biodiesel (B100) contains about 8% less energy per gallon than petroleum diesel. For B20, this translates to a 1% to 2% difference, but most B20 users report no noticeable difference in performance or fuel economy."
2. From U.S. Department of Energy: National Renewable Energy Laboratory: 100,000-Mile Evaluation of Buses Operated on Biodiesel Blend (20): http://www.nrel.gov/docs/fy07osti/40128.pdf
"The fuel economy for both petroleum diesel and B20 groups was 4.41 mpg based on in-use fleet data. An approximately 2% reduction in fuel economy for B20 was measured in laboratory emission testing."
3. From Pacific Biodiesel: http://www.biodiesel.com/biodiesel/benefits/
"I want my MPG!
Many alternative fuels have difficulty gaining acceptance because they do not provide similar performance to their petroleum counterparts. Pure biodiesel and biodiesel blended with petroleum diesel fuel provide very similar horsepower, torque, and fuel mileage compared to petroleum diesel fuel. In its pure form, typical biodiesel will have an energy content 5%-10% lower than typical petroleum diesel. However it should be noted that petroleum diesel fuel energy content can vary as much as 15% from one supplier to the next. The lower energy content of biodiesel translates into slightly reduced performance when biodiesel is used in 100% form, although users typically report little noticeable change in mileage or performance. When blended with petroleum diesel at B20 levels, there is less than 2% change in fuel energy content, with users typically reporting no noticeable change in mileage or economy.
Superior Lubrication for Your Engine
The injection system of many diesel engines relies on the fuel to lubricate its parts. The degree to which fuel provides proper lubrication is its lubricity. Low lubricity petroleum diesel fuel can cause premature failure of injection system components and decreased performance. Biodiesel provides excellent lubricity to the fuel injection system. Recently, with the introduction of low sulfur and ultra low sulfur diesel fuel, many of the compounds which previously provided lubricating properties to petrodiesel fuel have been removed. By blending biodiesel in amounts as little as 5%, the lubricity of ultra low sulfur diesel can be dramatically improved, and the life of an engine’s fuel injection system extended"
4. From GAS2: http://gas2.org/2008/04/10/biodiesel-mythbuster-20-twenty-two-biodiesel-myths-dispelled/#myth7
"FACT: Biodiesel contains about 8.5% less energy per gallon than petroleum diesel. For someone using B20, this means about a 1-2% loss in power, torque, and fuel efficiency. To put things into perspective, that’s about a 2 mph difference on the freeway if you were trying to go 55 mph. Millions of miles of onroad tests (aka trucking) have shown that B20 and diesel are practically indistinguishable. Biodiesel has also been used extensively in heavy-machinery, like tractors, loaders, and agricultural equipment, with no noticeable difference.
B100 users may notice a slight drop in fuel mileage based on the small difference in energy content, but torque and power are usually comparable. I’ve seen a 1-3 mpg drop in fuel efficiency running B100. As an FYI, biodiesel has the highest BTU (energy) content of any alternative fuel (falling somewhere between diesel #1 and #2). Energy content of various fuels (per gallon, low value of range):"
Regular Diesel Fuel = 128,500 BTUs
Gasoline = 125,071 BTUs
Biodiesel = 118,296 BTUs
Ethanol = 76,000 BTUs
In conclusion: in real world testing there is no noticeable change in power or fuel usage with fuel blends of B5 (5% bio-95% petroleum) to B20 (20% bio-80% petroleum). B100 (100% biodiesel did show a decrease in performance and fuel economy due to it's lower BTU value. The added benefit of increased fuel lubricity over the ULS fuel is a plus for the consumer in the form of possible lower maintenance/repair costs