Does anyone here fill up only with OnCue and has noticed reduced mileage from it? My last 2 fills have been OnCue on an empty tank, and I'm losing probably 40% of the mileage as usual.

Pretty sure it wasn't a recent switch to winter blend, and on top of that I'm getting their 100% gas and prior to these 2 tanks, the vehicle was getting the usual mileage.

Tires have adequate pressure, haven't been driving any differently than usual, and I'm calculating MPG by hand. (reset trip meter at every fill and then divide those miles by the number of gallons to top off the tank).