Premium Petrol or not?

[Gnasher]

We get 100+ RON out here in Cyprus and it's still cheaper than UK standard unleaded!! 

Not looking forward to coming back!! 

[GrahamFR]

Super unleaded does make a difference. You may have to run a few tanks to notice but your ecu will adapt to a better rate of fuel. The only real placebo is the super diesel stuff, that's just a con and won't improve derv performance, may help the engine last longer but that's it.

[corgi]

Super unleaded does make a difference. You may have to run a few tanks to notice but your ecu will adapt to a better rate of fuel. The only real placebo is the super diesel stuff, that's just a con and won't improve derv performance, may help the engine last longer but that's it.

It will not. A standard GTI is optimised for 95RON running it on 98RON will not develop more power as the timing will not be advanced to allow the engine to take advantage of it. It will not do any harm, short or long term but there is no advantage in running Premium Unleaded on the current Golf.

I have had previous experience with the Mk5 Golf Ed 30 and others (Honda S2000, Honda Integra Type-R etc.) which were optimised from the factory for 98RON but would run on lower octane - which were auto-detected by knock sensors which reduced the advance on the timing to eliminate detonation - with reduced performance...

Now if you want to remap you MkVII, you might re-map it based on Super Unleaded and you will see more power, and assuming the MkVII GTI has knock-sensors, you could run it on 95 (in this situation) with reduced performance.

The test that I have seen performed used an Impreza WRX (optimised for 98RON)...

[mullermn]

Last time this came up someone posted this, which is quite useful to understand why the higher octane number makes no difference in a car that is not tuned for it:
http://www.youtube.com/watch?v=D9nhXNarFdg

[Darlo]

Well what is confusing me is that the tests I have seen have been conducted on cars optimised to run on 95 yet still shown an improvement with 98? Think 5th gear has done a few bits on this and cars have always shown an improvement?

[mullermn]

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.

[Gnasher]

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).

[GrahamFR]

Sounds like only a dyno run will solve this. Anyone got any plans on dyno'ing there 95 RON Gti?

I did mine the other day, made 243bhp with BP Ultimate (Shell was closed due to tanker delivery).

No graph as its a before and after run so wont be getting one till the end of the month. All I do have is this...

[mullermn]

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).

Well that sounds fairly thorough, and I don't know enough about cars myself to come up with any explanation.

It could be that there is something other than the octane level which is different about the premium fuels which does make a difference? Just guessing though.

It would be nice to get a proper answer as I'd happily pay the little bit extra if it was better, but equally I don't want to be a mug and pay more for something that's just in my head.

[Gnasher]

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).

Well that sounds fairly thorough, and I don't know enough about cars myself to come up with any explanation.

It could be that there is something other than the octane level which is different about the premium fuels which does make a difference? Just guessing though.

It would be nice to get a proper answer as I'd happily pay the little bit extra if it was better, but equally I don't want to be a mug and pay more for something that's just in my head.

Probably right, one of the premium fuels gave hardly any more power than 95, but the others did.