Why does fitting wider tyres increase a car's emissions?

In your column 14 January, MV of Thatcham stated that "larger diameter rims increase exhaust emissions," but did not say why. I can see that average engine revs will be lower for the same journey average...

Should cars advertised with green credentials be advertised with laboratory fuel economy figures?

In your reply "Juke bucks jury" you highlight the discrepancy between laboratory fuel economy results and reality. The example showed an 80 per cent higher consumption than the laboratory and also, presumably,...

What do you think of the Toyota RAV4 Valvematic auto?

What is your impression of Toyota RAV4 2.0 petrol Valvematic automatic, please?

DSG versus manual for efficiency

In your list of CO2 emissions for cars I notice that the petrol Skoda Octavia vRS with DSG emits less CO2 than the manual version. Why should this be with exactly the same engine? Even more strangely,...

Did you know that you need special 'Umweltplakkette' stickers to drive in some urban areas of Germany?

With regard to your answer to the correspondent AH, Sheffield who was planning to drive to Germany, I don't know if you're aware of the fact that a great number of urban areas there have been designated...

CO2 emissions and wheels size

Could you please explain how and why larger wheel sizes increase CO2 output and consequently VED banding? The car still travels the same distance irrespectice of tyre size.

Does the new KIA Rio CRDi achieve Euro 5 emissions without a DPF?

I read that the new KIA Rio 1.1 CRDi ecodynamics (85 g/km CO2) does not have a DPF, despite achieving Euro 5 emissions. If that is true then it can only prove more popular for short journey motorists who...

Which automatic car would you recommend for 6000 miles per year?

I am looking for a suitable new car with automatic transmission for my wife. Annual mileage will be about 6000. Current models being considered are Astra 1.6 auto, Corsa 1.4 auto, and Fiesta 1.4 auto....

Wheels, tyres and VED

In June 2011 I purchased a new Mercedes E250 SE CDI Blue Efficiency with 7 speed auto box. The actual vehicle was in the local showroom on rather 'blingy' 17" wheels which I did not want for practical...

Seat Ibiza Ecomotive engine upgrade?

Looking at the Seat Ibiza brochure it appears that the Ecomotive CO2 level has been reduced to 89 gms and the max torque figure has been reduced to 1500. Is this correct as I tried this engine in a Polo...