I just had my oil changed. Cost was $45+ tax. (They wanted $40

for Tire Rotation, but I passed on this).
I was working on 47mpg tank, but at oil change, my trip meter was reset (by product of clearing service wrench?).
The second half of the tank after oil change, I averaged 41mpg over ~200miles.

The drop in mileage doesn't compute with me - Maybe breaking in new oil causes mileage drop...
Anyway, I am on a new tank and am back to 46mpg.

Maybe it was just an anomoly.
Did anyone else experience something like this?