Spaghetti Carbonerror?

I own a two-year-old BMW X3 3.0 Diesel Automatic. The 'birth certificate' for this car states it has CO2 emissions of 226g/km, which just puts it into the £405 tax band. Several websites quote a much lower emissions level for the car. I average mid 30s mpg with quite a heavy right foot and therefore I feel that the websites could be right. Is there any way I can query/challenge the tax band my car is in?

Asked on 3 July 2010 by SW, Wokingham

Answered by Honest John
No. Here are the VCA figures for your car, assuming first registered April 2008:
X3 3.0d - with particle filter M6 (Manual) Diesel 210g/km EU4
X3 3.0d - with particle filter A6 (Automatic) Diesel 229g/km EU4
X3 3.0sd - with particle filter A6 (Automatic) Diesel 232g/km EU4
But the fitting of bigger wheels with wider, lower profile tyres will increase the CO2.
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