This test compared smoke opacity readings with a measurement of particle numbers in the exhaust. The 2010 Euro 5 diesel vehicle had an aftermarket DPF fitted. The smoke test produced a low, repeatable reading, while the particle counter showed approximately 3.2 million.

A brief change to the engine ECU software did not lower the particle reading; some measurements increased. When the sampling tube was removed from the exhaust flow, the displayed value fell quickly. The test shows that a low smoke reading alone does not confirm that a DPF is working properly.

The team then tested a 2019 Euro 6 vehicle with a 1.6-litre diesel engine and its standard exhaust system. After the engine was revved, the device reading fell below 1,000 and sometimes reached zero. The video presents a specific comparison, not a universal vehicle inspection threshold.