871 oil mixing with fuel

[Waterloo]

My very first thought was Algae... I worked in the oil patch up in ND for a few years, and can tell you the fuel up there was expensive and crap. Most fuel was stored in above ground tanks, and not well maintained from my experience. Water from condensation was normal, but some outfits let it get out of hand, frozen fueling hoses were normal at a few places I fueled, and a real bitch in the winter. I can only imagine that more than a few of those tanks are infested with the algae and other forms of nastiness. Have the fuel tested like Rawze stated, but I would bet it is algae. If it is, time to stock up on the biocide and plan on treating at every fill up to keep it at bay, after the system is thoroughly cleaned out of the nasty critters.