What B5 is
B5 is a fuel blend with 5% biodiesel and 95% petroleum diesel. The biodiesel itself meets ASTM D6751 before it's blended in; the finished fuel meets ASTM D975 — the same specification that covers conventional diesel #2.
That last point is the important one. Since 2008, ASTM D975 has permitted up to 5% biodiesel content in fuel sold as standard diesel. Pumps don't need to label the biodiesel content unless it exceeds 5%. So a station selling D975-compliant fuel may be selling B0, B2, or B5 from the same hose, depending on what came off the rack at the terminal that morning.
Engine compatibility
Every diesel engine sold in the US accepts B5. There is no manufacturer who approves D975-spec petroleum diesel but excludes B5 — because the D975 spec itself permits B5. If you've been running ULSD without thinking about it, you've been running fuel that may already include some biodiesel, and your engine has been fine.
This applies to everything: light-duty pickups, heavy-duty trucks, agricultural equipment, marine diesel, generators, and rail. There's no compatibility carveout for older engines at the B5 level. The historical concerns about biodiesel and rubber fuel-system seals don't apply at 5% inclusion.
What changes (and what doesn't)
Practical effects of B5 versus B0 in real-world use:
- Fuel economy: no detectable change. Biodiesel has about 7% less energy per gallon than petroleum diesel, so a 5% blend is theoretically 0.35% lower energy content — well below what you can measure on a fill-up.
- Cold weather: no meaningful change. Refineries that blend B5 use the same seasonal cold-flow additives they use for B0.
- Lubricity: a small improvement. Biodiesel adds lubricity to ULSD, which is one reason refiners blend it in even at low percentages — modern ULSD without any biodiesel content can be marginal on the lubricity spec.
- Emissions: a small reduction in particulate matter and sulfur, proportional to the inclusion rate. Not transformative at 5%.
- Storage: no different from petroleum diesel for normal use. Biodiesel oxidizes faster than diesel, but at 5% the practical storage life is unchanged.
Where you'll find B5
Effectively everywhere diesel is sold. Because ASTM D975 includes B5 within the standard diesel spec, retailers and fleets handle it identically to petroleum diesel. There's no tracking or labeling requirement, and no infrastructure distinction.
If you specifically want a higher-percentage labeled biodiesel blend, our station locator shows the public stations selling B20 or higher (1,967 of them as of April 2026). For B100, see the B100 page.
Federal Trade Commission labeling
FTC rules require explicit labeling for biodiesel blends above B5, but not for B5 and below. A pump that's selling exactly B5 doesn't have to mention biodiesel content; a pump selling B6 or higher does.
If you want to confirm what you're buying, the bill of lading at the truck stop or fleet depot is the authoritative record. Retail customers can ask the station which terminal supplies them; that terminal will know the rack blend.