Unleaded or Super Unleaded

[SuprSi]

That's fair enough.

I think that only a car, several tanks of fuel and a dyno will establish the answer.

The only thing I'd suggest is the engine doesn't have a 'target' power output...

But isn't that exactly what a remap is? A higher target power output? I think that an ECU does work to a specified power output and will work with the currently available fuel and the currently available air to achieve it where possible. Anti-knock retardation only kicks in when the fuel is of unacceptably poor quality.

We could be talking at cross-purposes - or in violent agreement

Mostly in violent agreement!

Hmm. I'm reasonably sure (not 100%) that the figure audi specify is just what the engine happens to produce under optimal conditions. For example, the ecu software will have the ignition timing map which can only be retarded from standard, not advanced. And also a max boost pressure etc etc. Fueling is what it is, that shouldn't vary. These are just the standard parameters, and are basically what are tweaked in a remap. The engine can't see that it's over/under achieving and then ramp up boost and timing to get to the manufacturers specification. If I'm wrong I'm happy to be corrected.

[wildbore]

Interesting. I think I have reached the limit of my understanding of combustion science and ECU functions.

I do know a couple of people who might shed more light on this - time to consult some experts (I work in the automotive industry). Will post again if I find out more,

It's all fascinating, though...

[Leo-RS]

So now I will be making more frequent trips to the pump and having been driving my van and a few SUV for the last 4 years I now have the choice of different petrol.

What is everyone's choice when it comes to filling up and do you think there is much difference?

You must be joking right?

Why have you bought an Audi RS6 as by even asking that question you have shown you have little to no knowledge of the performance car market.

I could go into the whole 10% power loss thing, it's only 5ppl more or the cost of a ham sandwich on a fill but yeah, go fill your £90k highly tuned performance car on piss water, just don't be alarmed at the stares you will get at the pump from proper car enthusiasts

Ah Leo!! Glad to see someone is out there vetting everyone before they dare buy a super car! "Proper enthusiast" didn't know that was the criteria when I handed over all the cash to Audi! I hope when they find out they don't confiscate it and put me back in a diesel as punishment.

People like you " Mr I know everything" are the only ones who get laughed at pal with the only fun in your life coming from a car.

From the latest posts and through previous reading the whole debate comes up as there are different views on which fuel to use. Does it actually give you any performance increase or is it just another way off oil companies squeezing another £££ out your pocket.

Of course it does, have you ever been to a dyno day, do you follow tuners on instagram and facebook that test all of these fuels? MRC frequently post articles on the subject with 95 vs 99 differences, even using 97 SUL octane fuel will inhibit power.

An old article but illustrative of what benefits there are from super unleaded fuel...

http://www.pistonheads.com/gassing/topic.asp?t=302977

2 key snippets from the article highlighted below....

For the E46 M3 CSL the difference was even more pronounced. The difference between running 95 Octane fuel and a higher octane fuel from BP or Shell was very noticeable on the open road and the dyno confirmed this, the car did feel sluggish on the lower octane fuel

It is clear that older engines show a clear benefit of running higher octane fuel, but more modern, sophisticated engines have the ability to advance their fuel timing to take full advantage of this enhancement to a far greater degree. For the BMW M3 CSL the difference between running 95 octane fuel and Tesco 99 fuel was over 40bhp; that’s over 10 per cent

So a 380hp BMW M3 losing over 40bhp by switching to 95 octane. That is over 10% of its power output.

The RS6 has a 560ps engine, feed it 95 octane and you may well knock it down to under 500, and for what? The price of a ham sandwich?

Fill up at Tesco, use Momentum and the price is guaranteed to be 5ppl more than its 95 octane price. 5p be that in Fulham, Bradford or Inverness, it's capped at 5ppl more than 95. 70 litre fill = £3.50. An RS6 costs £80k+

My point was, why buy a high performance car and feed it piss water for the sake of the cost of a sandwich? You're losing a shed load of power, torque and response.

For sure, in emergencies, you can use 95 to get you to your nearest 99 station but I wouldn't be doing any full boost driving or top speed runs using 95 octane. The ECU will pull out boost and <beep> timing as soon as it detects knock and on 95, it most certainly will do. Higher octane allows for more sustainable boost, it allows for ignition advance and both of them make for a much better, quicker, more responsive car.

I'll ignore the rest of your drivel, just don't ask stupid questions like that again

[wildbore]

Leo, unless I am missing something, you are quoting figures for cars that are 12 years old or more. Those engines definitely were affected by fuel RON grade and nobody is disagreeing with you for cars of that vintage. I am not saying this as gospel, but I don't think that it is still the case that fuel will impact performance so dramatically.

[Leo-RS]

Older generation cars pre 2000 in general didn't have knock sensors so were unable to take advantage of higher octane fuels unless specifically tuned for it, cars from early 2000's though were fitted with knock sensors, more so for performance cars. The BMW M3 is a high performance N/A engine and it's evident from the results that it is able to adapt for fuel quality.

I have no idea what an RS6 would dyno on 95 octane fuel but I would put my house on it that it would make nowhere near standard output. If I had to put an estimate on it, probably around the 525 mark.

Audi themselves limit power on certain cars for markets that have poor quality fuel. A 2015 Audi S3 has 300ps here in the UK but only 275ps in South Africa. That's pretty close to the 10% I'm talking about.

If you're on Facebook, like and follow the tuners pages, (MRC/APR/Revo etc) There are lots of articles about owners using 95 octane fuel and the cars really struggling on the dynos.

[Edwardo1]

Wildbore how dare you question the mighty God of RS tuning who is the great Leo. Don't you know he and only he will allow questions be asked that he deems suitable and if he ever disagrees with you then you will be tarred forever with the " Non proper Car enthusiast" label .

He might have dissed the original post due as his ultimate knowledge of RS tuning is so advanced compared to us minions, but it has got the keyboards active and proves there are other opinions and views which are out there and can be openly discussed.

And Leo unless your some sort of admin I think ill keep the right to ask what ever sh@t I choose pal

[Leo-RS]

In all seriousness Edward, if the horsepower figures aren't all that important to you, the response and improved mpg is probably worth the 5 pence per litre more

[jezitalia]

Just dipping my ear in, I have no performance or evidence figures to add.

I take the view that it says the car prefers 98, but will drink 95.

If I am to believe the marketing humph, the higher grade fuels are cleaner and kinder on the engine.

As such I seek out Vpower or Momentum, even German/ Swiss 100 when I can.

If there is a performance gain, and an efficiency gain while using a kinder fuel, I conclude that using 95 is a false economy.

As has been stated before its Smiles per gallon, not the miles per gallon that matter and why many have the car.

[Ungjaevel]

Hey hey such a discussion and I was away all day

The stock RS6 *can* be run on 91 octane (refer to manual) and statements like
"If you gave the car a frequent thrashing on 95 I'm pretty sure you'd end up having a catastrophic engine failure within 5000 miles. The ECU can only compensate so much and knock/pre-ignition is very harmful."
are completely false. The ECU can and will handle anything they supply at the gas station.

98 is not "cleaner" or "nicer" to the engine. The octane level is the amount of resistance to self-ignition. On stock cars it's come-si come-sa if you run 95 or 98, but on a tuned car, well... it's tuned for the purpose. The difference is very clear. Stock cars have a requirement to start in -30* (I know because I live in Sweden ) so they can't be tuned too much - they wouldn't start under these conditions.

"I don't think that it is still the case that fuel will impact performance so dramatically"
Stock - I doubt 95vs.98 would differ that much. Tunes - very much so. Agree?

"Smiles per gallon, not the miles per gallon that matter and why many have the car." I think that sums this thread up.

[chunky79]

So now I will be making more frequent trips to the pump and having been driving my van and a few SUV for the last 4 years I now have the choice of different petrol.

What is everyone's choice when it comes to filling up and do you think there is much difference?

Ah, see the RS6 is a penis extension. Someone who knows anything about high performance cars would already know this.

This is the kind of reply you've given to others in the past Edudo.

nice penis extension though!

[Shinobi675]

They do 102 by the ring. That makes a difference to car feel and lap times. I normally only use 98 so I'd guess the difference is more than 95-98.

The cars more lively, I don't think I've got the feel to say more powerful, but certainly can get on it sooner.

[neilparf]

VBstard. All. The. Way.

[Shinobi675]

I like the fact tesco 99 is cheap! But I can't be bothered to drive there so normally it's the first shell after 200miles of the last!

[RossDagley]

Generally a full tank of super will pay for its difference compared to a full tank of regular with the increased MPG.

Plucking some rough numbers:

300 mile journey at 18mpg (my normal unleaded example), fuel at 117.81p/litre = £88.50 cost
Same journey, this time with 21mpg (super plus etc), fuel at 122.81/litre = £79.76 cost.

Obviously I don't know the mpg you're getting, or the exact fuel price, but a very slight rise in mpg makes a big difference in cost. Almost a tenner cheaper to get the super plus fuel once you've actually used it.

[SuprSi]

Hey hey such a discussion and I was away all day

The stock RS6 *can* be run on 91 octane (refer to manual) and statements like
"If you gave the car a frequent thrashing on 95 I'm pretty sure you'd end up having a catastrophic engine failure within 5000 miles. The ECU can only compensate so much and knock/pre-ignition is very harmful."
are completely false. The ECU can and will handle anything they supply at the gas station.

98 is not "cleaner" or "nicer" to the engine. The octane level is the amount of resistance to self-ignition. On stock cars it's come-si come-sa if you run 95 or 98, but on a tuned car, well... it's tuned for the purpose. The difference is very clear. Stock cars have a requirement to start in -30* (I know because I live in Sweden ) so they can't be tuned too much - they wouldn't start under these conditions.

"I don't think that it is still the case that fuel will impact performance so dramatically"
Stock - I doubt 95vs.98 would differ that much. Tunes - very much so. Agree?

"Smiles per gallon, not the miles per gallon that matter and why many have the car." I think that sums this thread up.

Didn't someone recently blow their C7 engine that had been using 91 RON?

And are you sure that figure you found in the handbook is RON and not the American MON?

I concede that you will probably not screw your engine on 95.