[milesr3]

I run my 535d exclusively on V-power diesel. Shell don't make any claims about it doing anything other than keeping your engine clean, but BP do make claims about their Ultimate diesel producing more power (up to 8% IIRC). I doubt that they could do this unless they had proven it in 'normal' cars, which they have if you read the blurb on their website. BP state that their Ultimate diesel produces less soot as well, which is going to lead to fewer DPF regeneration cycles.

On the butt dyno the V-power has better part-throttle response and is noticeably quieter at startup compared to regular Shell diesel extra. I think I get a bit better mpg too, but I've never measured it scientifically.

The extra few quid on a fill-up is insignificant to the purchase and running costs of these cars, so why not use the best fuel you can? My father-in-law always buys the cheapest supermarket diesel he can (Tesco/Asda) and just had to spend an order of magnitude more than he's saved on fuel having the fuel pump housing removed from his Focus and all the accumulated crap cleaned out because he was getting fuel starvation. And wasting time and money having the injectors cleaned by a 'specialist' beforehand, which made no difference.

I would be very interested in seeing some dyno results of standard and remapped BMW diesels on regular and high cetane diesel as well.