Severe gas mileage drop after recall work (sounds crazy, please help)
 

I drive a 2010 RS 7.0 and my usual fill up would show 290-305 miles until empty and would yield roughly 285-300 actual miles per tank. Eight months ago I had the oil consumption recall done and noticed that my miles until empty gauge would go to EXACTLY 273 miles EVERY single time after a fill up. I started keeping track of my actual mileage per tank on the "trip A" gauge and was only getting 260 miles per tank maximum. Dealership had no idea why the sudden drop and had no answer other than the bottom end of the engine needed to break in. Flash forward to a month ago when I had the airbag recall done for the second time. Suddenly at each fill up, my range until empty gauge goes to exactly 257 miles now for the last 4 tanks and my ACTUAL mileage has dropped to a ridiculous 227 miles per tank getting around 15 mpg. Again the dealership has no answers and looks at me like i'm crazy when I try to explain this happening after the airbag recall. I realize that the recall should have ZERO effect on my mileage, but i'm just dumbfounded as to why the fuel range goes to the same exact number after every fill up as well as the drastic drop in overall mileage? One guy in the garage said that when the ECU is flashed, the car has to "learn" how to drive all over again. Anyone with any thoughts, input or answers to this quandary would be greatly appreciated. Thanks in advance.

Yeah, that sounds kinda weird. Instead of observing miles per tank, try calculating miles per gallon.

Example: You just filled your car with 10.729 gallons of gas. Your current trip meter reads 307.6 miles. Divide 307.6 by 10.729.

307.6 miles / 10.729 gallons = 27.6 miles per gallon.