I recently had to bring in my 2007 mini cooper for a recall on the converter and since then I am not getting the same gas mileage before I brought it in. I averaged aprox. 33 mpg now 29 mpg. Is the caused by whatever they did with the converter?
Take it back to the dealer and complain. The car’s performance should not be worse after the recall action. The dealer should restore your car’s performance to pre-recall repair condition, for free. If the dealer tries to charge you, or does the “dealer dance-around”, contact Mini Cooper, America.
How did you measure the mileage before and now? How many samples have you done since they did the service.
My guess is they had the battery disconnected long enough that it has gone into default mode and as it relearns it may have a little lower mileage and that in time (maybe a few tank full’s) it should return.