Why is our Vauxhall Insignia much lower in road tax than our Nissan Micra?

My son has just purchased a new Vauxhall Insignia diesel. I understand that there is no road tax to pay for the first year and that it's then £100 per year afterwards. Can you please explain why my wife's Micra 1.4-litre petrol attracts £165 per year road tax?

Asked on 14 July 2012 by AW, Rustington

Answered by Honest John
Because this particular Insignia has been NEDC tested as emitting less than 130g/km CO2 and the Micra has been tested as emitting between 151 and 165g/km CO2. The older a car, generally the higher the CO2.
Similar questions
A colleague has to tow a 1300kg trailer as part of his work on a daily basis. To get the right tow car he has to go for something which hits him hard in tax terms because of high CO2. He has posed the...
I currently drive a 2005 Volkswagen Golf Plus 2.0 TDI that has done 182,000 miles. What should I replace it with on a maximum budget of £12,000? I need a workhorse to do 20,000 miles a year (80 per cent...
I have £20,000 to spend on a small 4x4. What do you suggest I get? I like the petrol driven Mazda.
Related models
Cute looks. Not very different from the Fiat 500.
Superb ride comfort, excellent efficiency from the diesel engines, practical and spacious.