Do not be systematically against additives ...
I (a little) worked in the automobile and I tried various commercial additives too.
Some products are very effective and most of them correspond to a very specific use.
Anti-friction additives using, for example, "silicone oil", are remarkable if used as soon as the engine is finished breaking in.
Motorists ATTENTIVE to their consumptions note a decrease in consumption between the purchase of the new vehicle and a mileage varying between 10 and 30.000km. Then the consumption stabilizes.
I had in the hands of customers treated vehicles that were so amazing: no clicks, engine noise of V6 on a 4 cylinder and occasions and a significantly improved torque.
However, the gain in consumption, if it can possibly be measured, does not exceed the 10%, which is the gain that most econologist motorists can obtain with intelligent driving ...
I also used fuel additives, some of which were supplied for the first oil change by a major manufacturer. Here again the results were convincing. My BX purchased at 200.000km only worked in ON / OFF mode, it did not respond to intermediate throttle positions. The treatment brought the situation back to normal, but no gain in consumption ...
To conclude, these products contribute to the proper maintenance and longevity of a vehicle. Most of these additives are also integrated in high-end lubricants and fuels ...