Used in Opel Corsa D 1.3cdti with 30 liters of fuel (which is a stronger mixture than recommended - 1 bottle in a full tank). The car used to smoke when you pressed the gas pedal to the floor and was somewhat hesitant in acceleration. After using it, the smoking stopped, I noticed a noticeable difference in acceleration, and the engine's operation sounds smoother now.
Very honest for about 8 euros since I have used more expensive cleaners (10-12 euros) and they had similar, if not slightly worse, results.
The only negative is the cap, which has aluminum foil and is not easy to open. In practice, you have to carefully pierce it to avoid any pieces of aluminum foil getting into the tank.

I put it in a 2012 pounto multijet 1.3 with idle instability, I didn't expect miracles but from what I've seen it has done a very good job!

I had expected a check with an error indication on the 4th nozzle. I filled it with 20 liters of diesel and it indeed did the job. One month later, the check did not light up again