My service station uses old style fuel dispensers (from like the early 80's). We have 4 in-ground tanks: Ethanol Free, E10, Dyed Diesel, & Hwy Diesel. Every time we get a fuel delivery the E10 dispenser slows WAY down. Speed picks back up to normal when the fuel level gets down around 2,000 gallons. Filters have been changed, to no avail. Any help fixing this issue would greatly appreciated.