Most likely it was fuel flow.That's screwy! I'm too lazy at the moment to do the math, but there's a hella difference in btu/gal between 1 & 2. Those mpg numbers should be reversed! Reckon the additives were screwing up combustion that badly?
My truck has a restriction gauge. Truck ran down the road fine, but was pegging out the restriction gauge for much of the day this week when the fuel was super cold.
Additives supposedly change the shape of the molecules in bio, so they can flow through the filter. With our series 60's and the small micron filters, I think the shape changing is doing little to no good.