bonus for me..lol i like a bit of competition :P

Actually you were referring to "amateur/professional/manufacturer mappers". ;)

I never said it was "that" inefficient. What I'm saying is the net gains are minimal and purely dependant on application and other qualities of the chosen fuel. For the variety of reasons I chundered on about over the last few pages. Of which the critical key factors are annoyingly not publically quantified by the fuel retailers.

I never implied that, what I said was there is no such thing as the perfect engine. Thats not to say they are all poor. But if they were all that good, they'd have 99+% efficiency, produces 0g carbon monoxide and 0ppm Hydrocarbon (unburnt fuel) without the need for catalysts. The latter two components are the results of imperfect combustion, of which is a waste of potential power. Increasing the RON alone does not cure that - it never will, and manufacturers are yet to fathom a way to achieve this perfection. Currently resorting to power-sapping emissions control measures which just makes the engine even more inefficient (and less powerful).

I personally see the concept of manufacturer's recommending stuff open to interpretation; just like their recommended oils:

Porsche tell you to use Mobil oil.
Renault tell you to use Fina/Total
Seat tell you to use Repsol
Ferrari tell you Shell..they even "helped" to perfect Vpower (cough marketing bollox cough ).

....And Subaru recommend that you to use 5w30 in a new age WRX. Many Impreza owners/specialists will disagree with Subaru's recommendation :D

So why not extend it to fuel? So long as it meets the MINIMUM criteria, then there is no harm. Will the driver feel any difference? Is there any notable gain, be it mpg or bhp? If so, is it worth that gain?

(note: Before anyone jumps on the det bandwagon again, I said minimum criteria, I do not condone going below it without proper prior investigation).

There is an exception; E85 fuel. Whilst this gives a notable reduction in MPG (for the reasons I said ealier - it contains less energy). It is advantageous on a engine running extreme compression ratios (or turbo charged). With the right car (track-day special), this is currently the only exception I'll make. Unfortunately, even though its cheaper, its actually works out more expensive to run a car on it for daily communting, so its no good in a road car (nail in the coffin for Saab?). Inccidentally E85 burns faster than LPG , even though they have similar colorific values and RON - thats one reason why LGP can't make the same power increases. E85 also burns faster than petrol, its the speed at which it burns that gives the superior power advantage.

Or to put it another way: The waiter insists that I have the house Shiraz, when I'd rather have a Sauvignon to go with the Carbonara I've just ordered. ;)

Well we are clearly never going to agree and I think that 90% of what you are posting is misdirection. It all sounds 'clever' but does not really go to the point of the argument.

You say go with the minimum criteria - well for all the cars I mentioned there are cars in their ranges that have 98SUL as a minimum criteria. Even my humble Swift Sport. And those that did not heed such a 'recommendation' clog up the boards with stories of damaged engines.

BTW when I said 'manufacturer mappers' to me those are the guys that put ECUs into your car.

Do you have a single bit of evidence to support this?

I have never ever heard of non SUL being the cause for engine failure.

Swift Sports have a reputation for having damage to their engines with the one common denominator being non-use of recommended SUL. I got that directly from the Swift BBS - even more exciting than Snet.

Not to mention Japanese Import Subarus, classics were always melting things as they were designed to run high RON fuel and the quickest way to kill them was to use 95 RON fuel.

Check out the early years of this BBS.

I always remember reading an article in a car magazine several years ago, a guy with a version 5 STI, bought it (not sure if new or not), ran it on 95 ron and amazingly it blew the pistons to bits :lol1:
His excuse was that he was never told that they need super unleaded, on a plus side for him, he had it fully forged and an after market ecu then fitted.

Tony:)

So a Swift needs SUL?!

That's rather silly.

Not very good engines then, are they. :lol1::D

And your arguments lack any proper substance too. I do get to the point, and justify it with acceptable reasoning; you somehow fail to see that. :cuckoo:

Can you answer the question? If increased RON is of little value, as you contend, then why are there so many cars designed with engines optimised on higher RON fuel?

FFS just put in what is recommended in the manual or within the petrol cap."
The OP is asking about an R8.. :sleep:

Forged components won't resist knock.

Its a Compromise. They'd use E85 or E100 if given the chance; but current availability, taxation and economics don't support it for the end user.