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This publication is available at https://www.gov.uk/government/publications/mot-changes-from-may-2018-guidance-for-mot-testers/diesel-vehicle-emission-limits
Since 20 May 2018, there are stricter limits for emissions from diesel cars with a diesel particulate filter (DPF).
You must test vehicles to the manufacturer’s plate value (when present), or a new lower default limit for newer vehicles.
You must also give a major fault if you:
- can see smoke of any colour coming from the exhaust
- find evidence that the DPF has been tampered with
1. How to find the manufacturer’s plate value
The ‘plate value’ is the emission limit specified by the vehicle manufacturer. You can find it on the vehicle manufacturer’s plate.
It will be a number (usually in a box) and often at the bottom-right corner of the plate.
If there’s no emission value on the manufacturer’s plate or you can’t find it, you must use the new default limits.
In this example, the plate value is 0.52m-1.
In this example, the plate value is 1.82m-1.
2. New default limit for newer vehicles
You must test to these default values if there’s no emission value on the manufacturer’s plate or you can’t find it.
|Vehicle first used||Type||Value|
|1. First used before July 2008||Non-turbo||2.5m-1 or plate value if lower|
|Turbo||3.0m-1 or plate value if lower|
|2. First used on or after 1 July 2008||All diesels||1.5m-1 or plate value if lower|
|3. First used on or after 1 January 2014||All diesels||0.7m-1 or plate value if lower|
3. Diesel smoke meters
Diesel smoke meters should have been updated before 20 May 2018.
Contact the equipment manufacturer or calibration engineer with questions about update procedures for your equipment.
The Garage Equipment Association has published a list that shows which types of equipment can and can’t be updated.