[serialk11r]

I usually do notice the drop in mpg from winter fuel but I have never seen it drop this much, so I assume something else must have happened. I think the Raley's winter fuel might have been worse than the Costco fuel. I burned most of the Costco winter fill away driving into a 20mph headwind.

I can believe 4% variance in fuel. You can get that from more light hydrocarbons like butane/pentane/hexane and ethanol.

I have no way of properly measuring but I thought the mpg was extra bad when I was driving in freezing temps. Whether that's because the transmission fluid is more viscous, or if the engine coolant temp is low (it failed to get over 190F, so reduced timing is a possibility), I don't know. I'll probably add one more strip of tape to the grill in the winter to help it stay warm.