What would cause extreme fuel foaming on fill today?

It literally took me more than an hour to drizzle 36 gallons of diesel fuel into my tank today on fill valves that could be adjusted to a very slow rate.

The two unusual events were that:
(1) I ran it lower than I normally do before refill.
(2) This was to be sure and maximize the benefit of my one every 10,000 mile bottle of Ford Lubricity Additive that I just added to my previous fill.

I tried 2 different pumps at each of the 2 different stations that I visited. I have not dropped my tank yet to shorten the vent dip tube but historically only the last 5 gallons or so have been a PITA to get in.

This happened one time before several years ago in the winter when filling up in Ely on a trip to Idaho. I could not get two tenths of a gallon in without foam almost spraying back out and shutting down a very low flow adjusted fill valve. That time I just moved to another pump and it filled totally normal.

I am going to drop the tank and snip the vent tube and do some kind of fuel pickup mod when things slow down for me.

Any ideas as to what happened today? /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/confused.gif