Diesel cars face stricter emissions test in the changes to the 2018 MOT

What you need to know about the MOT test changes

Diesel drivers have been advised that their vehicles will face stricter emissions tests from 20 May 2018, as well as new categories that are being introduced to ensure maximum safety and economy. Following much recent media coverage on the true cleanliness of diesel vehicles and the safety of British roads, the proposed changes have been welcomed by many motorists. So, what are these new rules and how do they affect drivers?

A stricter smoke test


Cars and vans emitting clouds of black smoke will no longer be a sight on British roads when the new rules come into play. Such vehicles are releasing a harmful level of pollution due to faulty diesel particulate filters, which when working inefficiently can increase particulate counts by up to 20 times.


Since 2014, MOT testers have been required to ensure the original DPF is in place as some motorists were removing them, but now they will be tested for functionality as well. As a result, if the diesel has a DPF that emits smoke of any colour, it will automatically fail the MOT. In addition, if the canister is found to have been cut open and re-sealed, the vehicle may be refused a test unless its owner can prove the damage was caused by legitimate filter cleaning.


New MOT fault categories


Another change concerning all vehicles will be introduced alongside the stricter emissions test for diesels. Categories will now be implemented to identify the severity of an issue, and it will be within the tester’s remit to determine the seriousness of a problem. The three fault categories are:


Minor defects: these have no substantial impact on either the vehicle’s safety or the environment. A test certificate will still be issued.


Major defects: these affect the safety or environmental competence of the vehicle, or may put other road users at risk. If found, the vehicle will fail its MOT.


Dangerous defects: these pose a direct and immediate risk to road safety or the environment. If found, a certificate will not be issued.


It is hoped that these categories will lead to both improved safety and enhance driver responsibility when it comes to vehicles being out on the road. The classification of the most serious defects as dangerous will force drivers to fix such issues as a matter of urgency, since they won’t be able to drive without an MOT certificate. With many service centres able to fix faults and retest on the same day, however, the inconvenience of being off the road is limited.

Vehicles of 40 years old or more

A final change is that from May, most vehicles that are 40 years old or more will no longer need to take an annual MOT to confirm their road worthiness. However, if the technical elements of the vehicle’s main components have changed – namely the chassis, monocoque bodyshell, suspension, steering and engine – an MOT test will be required.

To find roadworthy used cars for sale, contact your local dealer.

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