B2 is more than enough to achieve the lubricity benefits of biodiesel. It provides the highest gain in lubricity for the lowest cost. Some 'premium diesels' include concentrations as little as .15%, just for the lubricity benefit.

When you buy B2, its not good because you are buying biodiesel so much as its good because you are NOT buying extra sulfur and lubricating additives. Biodiesel lubricates great, and is a fuel in its own right. Sulfur and other additives lubricate, but are not fuels, and make bad things (like sulfur dioxide). Nearly all diesel fuel in Europe (I think) is now B2, for just that reason.

However, it is a bit annoying that the pump doesn't say what the blend is.. Less than 5% is usually just called an 'additive', its not usually called biodiesel. If someone is calling it Biodiesel at the pump, personally I'd expect it to be at least B20. You might mention this to the manager. Express your happiness that they are supporting biodiesel, but suggest that the sticker on the pump show the concentration, so people know what they are putting in their tanks.

Peace,
Sam