Yes I've driven both many times. A friend of mine who used to own a 4.8is and has owned an M5 for the past year is selling his car due to the shocking fuel economy (and small tank). An M5 makes even a 4.8is look environmentally acceptable..

p.s. M5's chassis was good for a saloon but I found the M6 a little floaty, both of them were enjoyable though. Their main weakness dynamically speaking is the steering which feels artificial and synthesised - not a patch on the X5 I'm afraid. I have an E92 M3 on order and I'm genuinely concerned about how it will steer. Are you listening BMW??

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