Data from fuel quality inspections conducted by the California Energy Commission at M85 dispensing stations indicated that significant contamination of M85 fuel may be arising from the station fuel dispensing equipment. Repeated testing revealed that high conductivity and high color occurred in the first liter of fuel drawn from a dispenser after not being used for more than 6 hours. As the dispenser hose was the most likely culprit for causing the dark color noted in the first liter of fuel, a study was conducted to ascertain the impact of dispenser hoses on M85 fuel quality. Three types of M85 dispenser hose were tested: the standard M85 dispenser hose (Goodyear Maxxim M85), and two experimental Goodyear hoses with nylon inner liners (Nylon Veneer 66 and Nylon Veneer 11). The results indicated that the standard M85 hose contributed significant amounts of plasticizer (phthalates) and filler (zinc oxide) to the M85 fuel, and that this contamination could contribute to fuel filter clogging problems. It was also found that at least one of the experimental hoses (Nylon Veneer 11) demonstrated significantly less contamination potential than the other two.In addition, analyses of FFV sock and in-line fuel filters showed build-up of metal organic salts possibly resulting from fuel additives, metal corrosion and hose plasticizer acting in concert to form filter clogging material. Some additives act as chelating agents for dissolved metals, while plasticizers can create organic acids that together may form metal organic salts. The combination of amines (from additives), organic acids (from dispenser hoses) and metals (from corrosion) seen on clogged filters show strong circumstantial evidence that the synergism between additives, plasticizers and corroded metal ions form filter clogging material.