I really don't know what we have over here as underground storage tanks, but suffice to say they must comply with Western European standards.
Fuel will be of low sulfur content too. Some of what I got was E10 (10% ethanol), but even standard fuel has, by law, 5% ethanol content. Volvo says E10 is fine for 1976 and later model years (which is much older than most other brands will specify), except for directly injected (GDI) engines, which the B200F in my 245 obviously isn't.

The fuel looks quite okay to the naked eye and with negligible deposits in the tank, even after 25 years. It must be down to very fine particles that the oil refineries don't filter out.

All the fuel that filter has ever seen was filled at pumps in The Netherlands, Germany, Belgium, Luxemburg and Austria. Some of them were the big boys like Shell and Esso, others were discounters. So no dodgy Eastern European or Russian stuff.