When my 4.8 lease was up last year (2 year lease), I went with the diesel. One year later absolutely no regrets. The torque is great and only over 75 mph do I feel the difference in HP. The gas mileage is so much better that it is no comparison and the updated iDrive is much, much better. I also have not had an issue with the battery drain or surging (though the latter was not much of an issue for me). The sound IS different but I can live with that.

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2012 F10 550xi Carbon black/oyster
2011 E92 M3 SSII/black
2012 W166 ML63 Steel grey/porcelain
2007 E93 monaco blue/beige (retired)
2010 E70 35d Space grey/saddle brown (retired)