Excess exhaust-emissions levels account for more than a quarter of all MOT failures, with a marked difference between petrol and diesel cars.
Figures released by Redex, which evaluated the data that is submitted to the Vehicle Operator and Services Agency by every MOT test facility in the UK, show that some 26.2% of vehicles fail for this reason.
Significantly, 9.7% of petrol cars that were tested failed to meet the required emissions standards compared to 3.9% of diesel cars.
Bruce Ellis, research and development manager at Redex, highlighted a number of possible explanations for the difference in MOT emissions failure rates between petrol and diesel powered motors.
He pointed out that diesels operate at lower engine speeds and are therefore a little less stressed than their higher revving petrol counterparts, plus petrol cars are assessed for a high number of gases and hydrocarbons in the exhaust emissions while diesels are only tested for smoke levels.
The data shows that 47.97 million MOT tests were taken over the full year of 2010 and the first nine months of 2011.
A total of 14.43 million MOT test failure reasons were recorded during this time, including many that increased the risk ofbreakdown .
Copyright Press Association 2013