Diesel cars have come under fire in recent days for their polluting emissions, but should owners be financially penalised? After all, just a few years ago, people were urged to switch to diesel cars precisely because of their low CO2 emissions, which supposedly made them more environmentally friendly than their petrol-powered counterparts. We bought our diesel Peugeot 207 in 2008 for that very reason, confident that we were doing our bit for the planet. We were also attracted by the fact diesel cars were cheaper to run than petrol cars – good for the environment and low cost, what could be better? We were far from alone in seeing the appeal of diesel. Less than 7.4% of all cars in the UK were diesel in 1994, but by 2013 this had soared to 34.5% of the total, with 10.1m diesel cars on the roads. Yet now diesel cars are being ‘demonised’ for their harmful nitrogen dioxide emissions.