Why do you favour petrol over diesel?

Reader questions What Car?'s preference for petrol-engined cars over diesels in many car classes...

New Volvo XC40 vs BMW X1 vs Volkswagen Tiguan

Could you please explain why your new car reviews consistently favour petrol cars over diesels, even when it comes to SUVs? Diesel cars’ CO2 emissions are better than petrols’, as are your True MPG figures. 

The NOx emissions of the latest diesel cars that are fitted with AdBlue or other cleaning systems are also comparable to petrol counterparts'. Granted, diesels’ particulate filters do require regular longer journeys on faster roads, but this shouldn’t put off lots of people from buying a diesel.

Diesel particulate filters - everything you need to know

And if you add other characteristics of diesel engines, such as better torque and longevity, I’m somewhat baffled as to why an independently minded car magazine doesn’t recommend them more often. 

Richard Green

What Car? says…

We don’t favour petrol over diesel in principle; indeed, we still recommend an awful lot of diesel engines, including in our overall 2018 Car of the Year, the Volvo XC40.

Petrol is the obvious choice in small cars, because drivers of these usually won’t do enough miles to justify the higher price of a diesel. And with the progress of turbocharged petrol engines, this can also be true for larger hatchbacks and mid-sized SUVs. 

We also consider that many of these are run as company cars, and while diesels emit less CO2, they also incur an extra 4% on BIK tax. Plus, diesel models usually cost more than petrols, pushing up their P11D values, which the tax is calculated from.

It’s only when you get to large saloons and SUVs that diesel becomes the default. Often, a petrol engine won’t provide the flexible performance of a diesel in these, plus there’s a large disparity in efficiency.

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