It respect you will see little to none at all power gain wise or running wise difference between the two fuels, it's to cope with the difference in fuel types across Europe, etc, Ireland iv heard mostly sells 95-97? Correct if wrong get Germany is something like 102 standard. It is fine on a wide range.
Again, respectfully, I disagree.
Yes the engine can tolerate different fuel qualities, but you cannot expect it to operate at peak efficiency and power on 'bad' fuel compared to 'good' fuel.
The way in which an internal combustion engine "copes" is to ****** ignition when the ECU detects premature uncontrolled combustion occurring within the combustion chamber. When you ****** ignition timing, or implement any other coping mechanism, you lose efficiency and therefore you lose power.
Whilst fuels with higher octane ratings don't contain any more energy in them per unit volume, they do have a higher auto ignition temperature, and so are very much less susceptible to premature uncontrolled ignition.
The risk of this uncontrolled ignition goes up with increasing cyclinder temperatures during the compression phase. The ultimate temperature in the cylinder is directly coupled to the pressure achieved within the cyclinder (Gay-Lussac) and the temperature of the air fuel mix at the beginning of the compression stroke. If the temperature goes higher than the auto ignition temperature of the fuel, we will see premature explosive combustion, the ECU will ****** the ignition and we will lose power.
The S3 engine runs the sort of static compression ratio that only a few years ago would have been considered normal for a naturally aspirated engine. This 9.3:1 static compression ratio is accompanied by a 1.2 Bar of boost pressure, again, a level that is markedly higher than turbocharged engines of only a few years ago. The net result is an effective compression ratio of 20.3:1. A compression ignition engine will happily run at very high efficiency with significantly less compression than this, but we're asking standard pump petrol to wait until after we've achieved peak temperatures and pressures before we spark ignite it, and to please not auto ignite on the way there.
Thermodynamically and chemically that's asking the impossible, especially when you factor in high ambient temperatures or high altitude running. Yes, direct injection mitigates some of the issue, but were still seeing injection occurring some time before TDC on the compression stroke, so it doesn't remove the problem, and still doesn't allow sufficient time for the charge to fully stratify and be ignited by the spark, rather than be injected and immediately explode.
The use of high octane fuels in this engine will improve both power and efficiency, simply because the engine can wait until the optimum time to ignite the fuel mix, rather than having to ignite it early to avoid it exploding and damaging the pistons. Whether it's to a degree that you as a driver can easily detect or not may be debatable, after all, no one here can tell the difference between the 300ps and 310ps power units, but the physics behind it are by now fairly well established.
And 300bhp is hardly on the limit of high performance, yes 99 will be a little cleaner etc but honestly you aren't going to notice a difference in performance on a stock car
306bhp from 2 litres in a family hatchback with long service intervals and a warranty is something you take for granted far to easily. 153bhp/litre is extraordinary. Higher than a current 911 turbo.
Even 25 years ago, a 300hp engine in any form was something pretty amazing, but squeezing that much power from only 2 litres was next to impossible with any degree of assured reliability. A 300hp cosworth was an evil thing with all the subtlety in its power delivery of a brick through a window. Even in standard form with only 102bhp/litre, it wasn't exactly the sort of thing your granny could drive.
Modern NA stuff like the Lamborghini Huracan are 'only' 117hp/litre, the R8 only manages 100bhp/litre, so in terms of fuel requirements, those engines may be slightly less fussy when it comes to fuel. The now legendary Porsche 959 (the Veyron of the 1980's) had a specific power output of 155bhp/litre, almost exactly the same as an S3.
Michael Schumacher won his first F1 drivers championship with 185bhp/litre, and even now, the very latest Ferrari 488 is only pushing 171bhp/litre.
As I said before, if any engine was in need of a fuel with an enhanced level of resistance to detonation, its this one.
or not
(idk if its worth an extra 10p a litre)
had me worried 
