The Driver and Vehicle Standards Agency has issued an repeat warning to owners of diesel cars that the MOT will be more difficult to pass in two month’s time.
Changes to the roadworthiness test implemented from 20 May 2018 will include stricter checks of emissions from diesel vehicles fitted with particulate filters (DPFs), which are designed to trap harmful pollutants from escaping the exhaust pipe.
Under the new restriction, any vehicle fitted with one that shows any signs of smoke coming from the exhaust will automatically fail the MOT.
Diesel warning: Owners of diesel cars have been notified that their vehicles could automatically fail the MOT if there are any signs of smoke coming from the exhaust
According to motoring solutions provider MotorEasy, around six per cent of all cars that fail their MOT do so because of fuel and emissions faults.
However, that figure is likely to rise from May as testers are given free reign to clampdown on diesel vehicles in particular.
As well as being able to fail cars showing signs of smoke from the exhaust, any diesel that was originally supplied with a DPF and has since had it removed or tampered with will also flunk the test.
The DVSA said ‘legitimate work’ carried out on a DPF will have to be proven with a receipt from the garage that carried out the maintenance of the filter each time the vehicle undergoes an MOT.
The Department of Transport agency said the clampdown on diesel would ‘help improve air quality’ as well as keep vehicles safe to drive.
However, with many drivers unaware that the changes are afoot, the DVSA has issues test stations with posters outlining the test revisions from May.
The raft of new checks mark one of the most significant updates to the MOT since it was introduced almost 60 years ago.
Any vehicle fitted with a DPF will be checked to see if the filter has been removed or tampered with. If so, it is likely to be listed as a major defect and therefore fail the MOT
The DVSA’s update to the MOT is one of the most significant in recent years
Other new appraisal that will be conducted along with DPF from May include an inspection of emission control equipment and signs of fluid leaks that could pose an environmental risk for all cars.
There will also more tests for vehicles that are less than a decade old.
This includes scrutinising of reversing lights for any car registered from September 2009 and the daytime running lights and front fog lights for all cars cars first used from March 2018 – though these latter checks won’t first occur until March 2021 when these vehicles undergo their first MOT after three years.
All defects will also be categorised by a new description structure, which spans from ‘dangerous’ to ‘major’ and ‘minor’ issues.
Only minor faults will be passable – though will need to be fixed before the next test – while a major problem will result in an automatic fail of an MOT, which costs a maximum of £54.85.
If defects are classed as dangerous, the vehicle will not only flunk the test but should not be driven away from the MOT station until the problem is rectified, the new rules explain.
Around 6% of vehicles fail the MOT because of emissions faults each year, according to MotorEasy. That figure is expected to rise as a result of changes being introduced in May
Posters will be displayed in MOT garages about changes to the test being introduced on 20 May 2018. It notifies drivers of diesel cars of new emissions checks and explains the new fault categories
Agency chief executive, Gareth Llewellyn, said the changes were the ‘DVSA’s priority’ to help keep vehicles safe to drive, though many will argue it’s another stone thrown at diesel, which is already facing surcharges and taxes under new government rules.
Llewellyn explained: ‘The MOT test checks that important parts of your vehicle meet the legal roadworthiness standards. These changes to the MOT test will help make sure vehicles are safer and cleaner.
‘I’d urge all motorists to familiarise themselves with the new items that will be included in the test so that they can avoid their vehicle failing its MOT.
‘To be safe and responsible motorists should also carry out simple vehicle checks all year round.’
As well as the new checks that are being rolled out from 20 May, all vehicles over 40 years old will be exempt from having to undergo the annual roadworthiness check from the same deadline.
That means some of the most iconic British motor cars will no longer need to be scrutinised each year, with the DVSA claiming that these vehicles are now owned by enthusiasts and collectors who maintain them to a high standard themselves.
What is a diesel particulate filter and how do I maintain one?
A diesel particulate filter
A diesel particulate filter is a device that captures and stores harmful exhaust particulate matter to stop it from being released into the air we breathe.
But because they only have a finite capacity, the trapped emissions periodically have to be emptied or burned off to regenerate the DPF.
In real life driving terms that means making sure a diesel car gets a prolonged motorway speed run regularly.
This regeneration process removes the excess emissions soot clogging up the filter, reducing the harmful exhaust emission and helps to prevent the tell-tale black smoke you used to see from diesel vehicles, particularly when accelerating hard.
Euro 5 exhaust emissions legislation introduced in 2009 to help lower car CO2 emissions effectively made DPFs mandatory, and since then, around one in two new cars a year are diesels with them fitted.
There are two methods of maintaining a DPF – passive and active.
Passive regeneration occurs when the car is running at motorway speeds for half an hour or longer to push the exhaust temperature higher so it can start the process of burning off the excess clogged soot.
Active regeneration means extra fuel is injected automatically, as part of the vehicle’s ECU, when a filter reaches a predetermined limit (normally about 45 per cent) to raise the temperature of the exhaust and burn off the stored soot.
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