I have used optimax in every performance engine i have owned after reading the independant test report when it was launched.
If you speak to anyone in VAG who knows about fuel they will recommend it! Porche even print it in their UK handbooks!!!
I bought a Mk3 2.0 8v which was running on regular and after about 5 tanks the difference was very noticeable. I would point out it wasn't instant. But after a good month of using it there is an increase in performance and the whole engine runs smoother!
One of the biggest affects, which only one of you has noticed, is your engine burns a lot less oil, mine burns almost none atall. This is because the additives in the fuel reduce engine wear and keep things nice and clean.
It is slightly more money but if you do the math on the improved mpg it definately breaks even, if not works out cheaper than regular unleaded. Also less engine wear = less oil and reduced servicing bills, greater engine life.
I do not work for Shell. But have had a great deal of experience when it comes to fuels! This is by far the best available and the only draw back is you need to live near a Shell garage. It would be nice if other fuel suppliers produced a performance fuel and we could follow the Germans upto 100 ron!
Definately no placebo here! If you don't notice the difference then your engine is in a worse state than you realise!