Skepticism feeling ...

Well, I am (also of the reviews) have been very skeptical about the statements with regard to the alleged effect of the system cleaner. Still, I wanted to make my own opinion.
Prefixing them I need that some observations on pure emotion based, as I make no objective measurement conditions and can actually carry out objective measurements.
Engine: 2L vacuum cleaner with 150 hp (6 years old)
Before filling the tank, I filled completely. Then the cleaner purely poured (the application description on the tin really foolproof!).
The first thing I noticed, the engine runs more quietly!
Of course, immediately after the time of filling, but after 3-4 start / drive operations, slowly but surely.
I noticed is that since I was used to that, especially in the cold season, otherwise the engine a little louder than usual "rattles".
By that I mean with "quiet" not only the noise level, but he also runs "round" / resistance poorer.
Meanwhile, I take the 3rd tank after adding (mentioned reach approximately 2,000km).
The second thing I noticed, the engine pulls in the upper speed range of liberated (from approx 4.000U / m). Even this is not immediately after filling, but after two or three trips. These things I have especially noticed in 5th gear because of the acceleration process from 160 km / h tangy precedes than before. Here I believe also to be noted that the throttle response is carried out more easily. The maximum speed is reached more quickly than before.

Now perhaps the most debated point: fuel consumption.
My driving profile has not really changed over the previous ridden kilometers. (Relative equal distances in the week) Relaxed and foresighted driving on highway and in the city alternate with fast driving onto the highway. Especially on the highway, I believe, determine less consumption.
In general I feel that with my driving profile, the fuel consumption has lowered generally slow somewhat.
I had in-described driving behavior during the winter months usually an average fuel consumption to the 9L / 100km (even before filling the cleaner this year), so I reach currently approximately 8L / 100km.
After adjusting this to the certainly one or the other inaccuracy, as will become apparent to me still an estimated 0.5 liter less fuel per 100km. I can compare the again until after the current 3. tankful the 2,000km range of the product are exceeded. From the 4th filling should possibly be. The observed benefits run back into its opposite.

As I said, very much based solely on feeling, because I can not measure it.
Because of gefühleten changes to the previous state I am, however, (without knowing exactly what he doing exactly) very pleased with the cleaner!

Supplement 02.10.2015
Now that I have compared a year and no, I still come to the conclusion that it is with me (it is the emphasis) has come to fuel savings through the use of the additive.
Mind you I have in mind that after passing through the tank filling, the next (after pouring the additive) consumption was lower in direct comparison 2000km later, when everything was definitely through.
After consumption of the filled-additive of between consumption went slowly back up. But Here I emphasize, I am talking of 0.5 - 1 liter more per 100km.
Even now currently in the winter when driving through snow and ice to reach an average of only a maximum of 8,0- 8,2l. I am satisfied with.