I always felt sorry for the real refinery mogas blenders. Lots of components, crappy price forecasts, pressure to hit octane with nil giveaway etc, etc. And by the way, never run out or have tanks too full.

Prior to my current job (Process Engineering Team Leader over North Sea projects), I was doing blending and scheduling in a refinery in Montana. I have done a few hundred gasoline blends over the past few years.

You are correct that octane giveaway is a constant concern, and units are tweaked to balance everything. But the vast majority of the difference in summer and winter blends boils down to butane.

You should post here more often. We need more people who understand the energy industry and are willing to share that knowledge. Of course you may get the occasional "Big Oils sucks, and so do you", but most people here will engage and are seriously interested in learning new things.