Confused.com

Had a run out this afternoon and covered about 60 miles. As soon as I set off the display was showing 62mpg!! And that was the best I saw all day!!
How could it drop from 70mpg the other day (65mpg when I opened it up a touch for a mile or so) to around 60 mpg today.
Granted I was 2 up but being 2 up previously has never made that sort of difference, maybe a mile or two mpg but that's it.
Both rides (other than the little blast) were done at normal speeds & throttle actions to my usual riding style.
Is it possible that the ECU was initially confused with the new Super the other day and once switched off, then back on today 'reset' it?
I did however still think it was running better, not as in faster or better acceleration but just smoother. As per my previous post, I didn't say anything to Deb about my thoughts until we were a few miles from home. I had tried to replicate what I thought she was asking about, speed/gears/rpm by swapping about a bit. She remembered asking me the question about 'what gear I was in' and suggested today that she never noticed anything untoward.
Although in my mind I do think there is a difference in running I also think it's in my head, trying to convince myself the cost of the 'super' was worth it.