I'm running an F30 320dED, now on 8000 miles with 6000 of them mine and an average of 64mpg (brim to brim calculated). I abused it in December with four consecutive short runs to and from the airport in cold weather, and on the last run I smelled and felt the DPF regenerating (a very hot 'burning' type of smell). So I guess even if stuck in traffic (actually no traffic in the Olympic lanes) your car would have been regenerating properly. F30s are outstanding cars, streets ahead of anything else in the class. All the faults of the E90 put right in a much better looking car.