I think a good thing to add to the site (not something I have seen in your FAQ, although I easily could have missed it) is the minimum cetane rating for common fuel stations.
After much prodding at my local Sunoco, I found their minimum rating is 40 cetane - I had trouble finding that information elsewhere.
I wonder now with ULSD everywhere if the min cetane rating has changed from the tdiclub listings. (Some were rated at 52 cetane minimum, I'd like to know if that is still the case).
Also, biofuel locations could be helpful.