I actually have to agree with Dennis55 here...to an extent.

I have been using Dyno-tab for quite a while now. Not to save fuel, but to increase FUEL OCTANE GRADE.

I think people who wants to save petrol can forget about it. Most of you are right...your right foot is your fuel saver.

BUT I have to give the Dyno-Tab credit for its ability to improve the fuel.

I use it on my CX-9 that has been remapped for higher performance with higher flow air-intake. Initially, my engine has pretty bad 'knocking' whenever I put it under heavy acceleration between 4000 to 4500rpm. It slows the car down and renders the remap useless, as the ECU kicks in and dials down the timing due to the knocking. And this is with our RON 97 fuel.

So I started experimenting with Octane Boosters and all the additives that are around. Tried 2 or 3 bottles or packs of everything with various combination. Some required a lot to improve the fuel octane to a point that my engine does not knock.

Then when I finally tried Dyno-Tab 1.5grams octane booster, that was the solution for my car.

I use RON95 now with 2 x 1.5grams per fillup of 50 litres. No knocking. And I have tried this a few times. All brands RON 97 fuel makes my engine knock, without any additive. Some more than others. But with Dyno-tab and RON 95 fuel, I have not had any knocking when I stress my engine.

If you are looking to improve performance from your fuel, it works. And so do other octane boosters, but on my car, this works magic at a reasonable price level. I use it in combination with Miller Oils injector cleaner/octane booster. Even with these 2 additive and RON 95, it works out to be around RM 2.35 to 2.40 / litre in total (with Ron 95 at RM1.90). Still cheaper than RON 97, even at the new reduced price, and I get a better performance fuel.

For cars that are not tuned for higher performance based on RON 97, then not much use. It only really works if you run an engine that has been tuned for higher octane fuel but automatically reduces advanced timing when knocking is detected due to lower grade fuel. Therefore, when you improve the fuel grade, less knocking is detected and you get improved performance due to the increased advance timing of the spark plugs.

It's been retuned with leaner AFR ratio and advanced ignition timing. Knocking is very audible.

Similar with my S-max. Mine is 1st version at 200hp. So I remapped it to 240hp.

But I get knocking between 2000-3000 rpm with ron 97 fuel as well. For this car, I use ron 97 fuel and add 1 x 1.5 gram dyno tab and that almost completely remove all knocking phenomenon. Only under very special circumstance can knocking be heard. Of course there may be some very minor knocking that cannot be heard by the ear. But engine knocking that can be heard is really not something I want my car to experience on a regular basis.

I am not sure what parameters your tuner adjusted but I would first identify the rpm range in which knocking occurs. Then inform my tuner. Definitely will gave run a richer AFR with reduced timing. I would also have him increase tip in enrichment and check maf sensor calibration. Just some suggestions for trouble shooting.