In the UK, the emissions tests as part of the MOT for diesels is a smoke opacity test. Turbocharged vehicles have a limit of 3.00m-1. Up to six acccelerations are allowed where the three best results are averaged and should come under the limit. If you get less than 1.5m-1 on the first acceleration, then you automatically pass with a "fast pass".
On the right are the results from 6 years' of MOT tests with my 300Tdi. The catalytic convertor has been removed, as has the EGR. The oil is changed every 6-9 months along with the filter. Before the MOT, I take the car for a 20 minute run at motorway speeds to get it nice and hot. What has impressed me is that the emissions have stayed very good over time!
Here are the results:
- 2011, 148k miles - 1.58m-1
- 2012, 152k miles - 0.25m-1
- 2014, 159k miles - 0.39m-1
- 2015, 166k miles - 0.88m-1
- 2017, 170k miles - 0.74m-t
- 2018, 181k miles - 0.54m-1
NB: Some of the results sheets show the wrong test limit of 2.5m-1, as the garage would sometimes put the vehicle through as "non-turbo". The vehicle always beat this so I never brought it up.
