Comparing emissions: Old A5 vs new Q5

I've just received my new V5C document for my new 2014 Audi Q5 and I was comparing it to my Audi A5 with the same engine size, albeit from a 2009 vintage.

The CO2 reading for the new Q5 is 169 G/Km and the older A5 182 G/KM which is what I would expect with improvements in engine design and emission controls.

However,looking at the Q5's CO this is 0.244, the NOx is 0.162 and the HC+NOx is 0.183.

The older A5's figures are, respectively, CO 0.209, NOx 0.109 and the HC+NOx is 0.138.

Am I understanding this correctly? The older model is actually better at all emissions other than the CO2, even though it is in a higher Tax bracket?

Asked on 25 February 2014 by Colin

Answered by Honest John
Yes, because the Q5 has bigger body with more frontal area. CO2 never was a perfect basis for vehicle taxation because it's easily cheated in the EC Tests, but it's the basis that has been chosen.
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