Why emissions and mpg differences ?

Faults and Technical chat for the Kia Niro

Why emissions and mpg differences ?

Postby chr1s » Mon Mar 27, 2017 8:14 pm

As a prospective owner, I am going through the specs for the different trim levels.
Can anyone tell me why the '3' and 'First Edition' have much higher official emissions (+15%) and much lower official mpg figures (-14% combined) ?
At first I put this down to wheel size, but the circumference of the tyres (205/60R16 and 225/45R18) is near enough the same.
Is it the extra weight/inertia of the bigger wheels, or extra loads on the battery (and the engine, to support charging) or is it something else ?
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Re: Why emissions and mpg differences ?

Postby djbobbins » Mon Mar 27, 2017 8:34 pm

18" wheels might be slightly heavier but I think the main effect is higher rolling resistance owing to the greater width of the tyre. 225mm wide = nearly 10% wider than the 205mm 16" boot, so more rubber to stick to the road. Good for going around corners maybe, but not helpful for economy.
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Re: Why emissions and mpg differences ?

Postby djbobbins » Mon Mar 27, 2017 8:37 pm

If it's any consolation, I puzzled over the issue and went for a "2" spec with ADAP, but if I could have had the "3" on 16" wheels I probably would have done. Will miss the heated seats in my current car :-(
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Re: Why emissions and mpg differences ?

Postby chr1s » Mon Mar 27, 2017 9:27 pm

Thanks. I didn't think about the extra tyre width. That makes sense.

I am considering getting a '2', but I have timed it badly with the changes to vehicle tax on cars registered from the end of this week. If I want to take advantage of the old emissions-based taxation I may have a limited choice of ex-demo and pre-reg cars. If I buy a '3' then I wanted to understand why it uses more fuel, although I don't see myself buying a '3' plus a set of 16" wheels - it would take several years' worth of fuel savings to recoup the cost !
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Re: Why emissions and mpg differences ?

Postby djbobbins » Tue Mar 28, 2017 9:09 pm

I think it'd only make sense to have the 16" wheels if you are a company car driver and it was going to reduce the benefit in kind charge and the VED as well as the fuel consumption. I suspect there is very little chance of the government allowing drivers to pay less tax as a result of changing the wheels on a car, so I opted for the 2 trim level with the published lower emissions figure.
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Re: Why emissions and mpg differences ?

Postby AlanHo » Wed Mar 29, 2017 10:22 pm

If you had bought a 3 and then put 16" wheels on, you would still be taxed as a 3. You cannot change the tax band after it is registered.

In fact you cannot change the tax band after it is imported because the VIN number allocated to the car in the factory is accompanied by its full specification for future registration purposes.
Currently March 2017 KIA Niro 2 Plus ADAP in Whte
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