after using my car as a daily driver round london i can honestly say i saw very little difference between the PE map and the MSD closed loop map round town.

this is because the car never really has time to get up to temps and just loses loads of fuel in the warm up stage. you also have to consider that the amount iof distance you actually cover in traffic is sweet FA with alot of starting stopping hill starts etc.....average journey from my old house to my folks in traffic, 15 mins 1.5 miles!

on the motorway though there was a vast difference, a jump from 220 miles (PE) to over 300 miles (MSD) to a full tank so this is where i saw the benefit

for a london commuter, either put up with the crappy mpg, or get a new car, closed loop wont solve your problems for short journeys.