52 MPG on my latest fill (also the longest I've gone between fills in many years):
Could it be the winter grade fuel? Is it due to winter weather conditions? Am I getting lazy in my old age and putting less effort into eco-driving? Am I using cruise control instead of driving with load? Did I use the car for some shorter trips that I might have biked otherwise?
Yes.
For comparison, here's the previous Mirage's fuel log - much better winter numbers:
