What you have heard on the TV and read in newspapers about not wasting your money is true for about 95% of people out there who own cars that are designed to run properly on 87 octane (regular) gasoline. When you start getting in to high performance vehicles, especially turbo models, then you need to use high octange gasoline which would be 91 octane in state and 93 octane in some other states. Designing a vehicles engine for 91 octane gasoline allows them to design to tigher performance tolerances and such, enabling the engine to run higher boost without detonation (engine knock) which could cause permanent damage to the engine. I believe the stock tune will take 87 octane for short periods only, just long enough to get you to another gas station with the right gasoline. It will also run at a reduced level of performance and prolonged use of 87 octane will likely cause permanant damage. Further performance engine tuning requires the use of 91 or higher octane or you WILL damage your engine. I believe that most of this is laid out in the user manual and is also printed on the sales documentation in the window of the car to some degree.