Hi. My friend filled up his 2.2 Turbo Diesel the other day with Shell V Power and on the way home from the garage the engine management light came on and it went into slow safe mode. He has since topped it up with Tesco Diesel and it now drives totally normal, power the same etc except the management light keeps coming on and going off and a black puff off sooty smoke blows out the exhaust when under acceleration. Any ideas? Cheers, Lee