I commute 96 miles round trip, and I've been doing it for a few years so I've got a pretty good read on road/weather influences and what my gauges normally say.

Last week I was at 67mph, no wind, 550F EGT, 6-7lb boost, 24.4mpg overhead display/18.84 actual MPG for the whole tank
This week I'm at 67mph, no wind, 500F EGT, 8-10lb boost, 22.7mpg overhead display/(no hand data yet)

All things being equal; the same EGT, + higher boost, + crappier mileage = winter blend diesel, right? I have to ask because I've never seen it drop-off as abruptly as in the past.
Any thoughts?

Thanks,

Adam