What is causing my Mercedes-Benz E320 diesel to smoke under acceleration?

I have a 2002 Mercedes E320 diesel automatic estate. It has done 115,000 miles and I now use mainly Shell V-Power or other brand fuel, but I have been guilty of using supermarket diesel in the past. When I need to perform 'kickdown', an enormous cloud of black smoke emits from the exhaust. My local garage told me its the turbo having a clear out and not to worry, but it happens every time I need to accelerate quickly. I use the motorway at least four times a week but only doing a 30-mile round trip each time. Should I have cause for concern?

Asked on 25 May 2013 by DE, Higham, Kent

Answered by Honest John
It might be the turbo oil seal, but if it was that then you would be using oil. Might be the valve stem oil seals, might be the injectors. If the engine is not using oil, try a dose of diesel injector cleaner added to the fuel. If it does what you describe during its MoT, it will fail.
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