Premium Petrol or not?

[Darlo]

Were they proper and rigorous tests or were they just 'try different fuels and drive it around a bit'?

I think something like this is prone to confirmation bias with human testing - you want to see an improvement so you find one.

Well, the first test done by fifth gear was done with a dynamometer(sp?) and a rig with separate jerry cans for each fuel with multiple runs on each fuel. The other test (also done by fifth gear) didn't have separate jerry cans but did do an ECU reset between fuels. All tests found a difference between 95 RON and SOME of the 98 RON 'super fuels' on forced induction cars (Golf GTI Mk5, Golf GTI Edition 35, Subaru Impreza) but no improvement on a naturally aspirated car (Renault Clio of some variety).

Yes these are two I have seen. As I've stated before that cars not tuned for 98 still produce more bhp despite being tuned for 95..... According to tests on a Dyno anyway

[GrahamFR]

Just had a look whilst filling up with shell nitro, it says min. 95 ron. In my language that means using 98 Ron is better

[kor0]

Well, not according to the manual.

Please see the generic Fuel page in your owner's manual: (155 in this Skoda one as I don't have the GTI yet)

https://mediaportal.skoda-auto.com/resource/documentation/manuals/en/Fabia/05-2011/Manual/A05_Fabia_OwnersManual.pdf

The bit that interests us GTI users:

Prescribed fuel - unleaded petrol min. 95 RON

Use unleaded petrol with the octane rating 95 RON.
If unleaded petrol with the octane rating 95 RON is not available, you can use petrol with the octane rating 91 RON in an emergency. You must continue driving at medium engine speeds and minimum engine load. High engine revs or a greater engine load can cause major damage to the engine! Refuel as soon as possible with petrol of the prescribed octane number.
Even in case of necessity, you must not use petrol of a lower octane rating than 91 RON, otherwise the engine can be severely damaged!
You can find further information on refuelling page 156, “Refuelling”.

Unleaded petrol with higher octane number

You can make unlimited use of unleaded petrol which has a higher octane number than the one prescribed.
In vehicles with prescribed unleaded petrol 95/91 RON, the use of petrol with a higher octane number than 95 RON does not result in a noticeable power increase or a lower fuel consumption.
On vehicles with prescribed unleaded petrol min. 95 RON, the use of petrol with a higher octane number than 95 RON does not result in a power increase or a lower fuel consumption.

Maybe someone who already has the GTI manual can confirm?

[GTI-7-Performance]

Well, not according to the manual.
<snip>

Maybe someone who already has the GTI manual can confirm?

That's what the manual says. In fact it's the same handbook for all Mk 7 Golfs...