I give it 4 stars because it may have applications.
I wanted to see how much it can reduce the smoke of a common rail Euro 4 engine without a DPF.
When the engine is cold at low RPMs before it builds up pressure, it slightly reduces the visible black smoke, I would say about 10-20%, and completely corrects it, making it white and transparent.
In a warm car and under normal loads, you would say that there is no visible smoke at all.
I added 150ml to 18l, so the concentration is 3 times.
To say that it will eliminate the smoke, it would need a concentration of around 3%, which is not economically feasible, but to pass the vehicle inspection with 2 bottles in the reserve and expensive diesel, you pass as if you had a DPF