A fuel question.

Duggy72

Registered User
Hello all,

I have read many threads regarding the benefits of using super unleaded so I'm not asking that question again.

When refuelling yesterday I noticed on my S4 fuel flap it said std petrol 91 ron or super unleaded 95 ron.

In the UK I believe that Shell fuelsave unleaded is 95 ron. Does this mean that the car thinks its on super unleaded? I believe that using super 97 ron or greater will only see greater power and economy gains but if the car thinks 95 ron is super then it will be achieving it's factory quoted power outputs with 95.

I'm not sure what ron the other main suppliers quote for their std fuel but I have read that Shell is 95.

Thanks.
 

Dippy

Registered User
The engine does not know what the octane is as such. Getting increased efficiency from fuel burn (be it as increased power or increased economy) is primarily a matter of ignition timing. As I understand it the S4 ECU has timing set for 95 RON. The ECU will act on knock sensors to allow the timing to ****** for lower octane fuel, but not to advance for higher octane. This must have been a decision at Audi during development.
With an ECU remap I believe that this process can be adjusted to allow timing advance for higher octane fuel, and that's why you'll see different power curves for different fuel (APR as an example).

So unless I'm wrong, you will see no benefit from using super 97 RON, 98 RON or higher in your S4 with the OEM ECU.
 

scotty76

Registered User
Standard unleaded is 95, VPower I believe is 99 (as is Tesco Momentum 99). Other "super" unleaded varies. Some are 97. You are correct the fuel flap states 91 min, 95 recommended. This is typically less than the 2.0T cars which are designed to be at their optimum using super unleaded.

In terms of how it works, the car should make the quoted figures on 95. The engine will adjust to different fuel grades so best to pick one and stick with it. If you're getting the car remapped it will need super by default.

On my standard S4 I found no fuel economy or power difference using super. Details here My S4 thread

My old B7 2.0T FSI fuel flap and manual clearly show these are designed from factory for super. The dealers don't make that clear to the punters as they don't like splashing out for super. So in effect many people are inadvertently de-tuning their cars.

IMG_20140604_1434372221.JPG
IMG_20140604_1431521881.JPG
 

Bristle Hound

Moderator
Staff member
Moderator
The engine does not know what the octane is as such. Getting increased efficiency from fuel burn (be it as increased power or increased economy) is primarily a matter of ignition timing. As I understand it the S4 ECU has timing set for 95 RON. The ECU will act on knock sensors to allow the timing to ****** for lower octane fuel, but not to advance for higher octane. This must have been a decision at Audi during development.
With an ECU remap I believe that this process can be adjusted to allow timing advance for higher octane fuel, and that's why you'll see different power curves for different fuel (APR as an example).

So unless I'm wrong, you will see no benefit from using super 97 RON, 98 RON or higher in your S4 with the OEM ECU.
Standard unleaded is 95, VPower I believe is 99 (as is Tesco Momentum 99). Other "super" unleaded varies. Some are 97. You are correct the fuel flap states 91 min, 95 recommended. This is typically less than the 2.0T cars which are designed to be at their optimum using super unleaded.

In terms of how it works, the car should make the quoted figures on 95. The engine will adjust to different fuel grades so best to pick one and stick with it. If you're getting the car remapped it will need super by default.

On my standard S4 I found no fuel economy or power difference using super. Details here My S4 thread

My old B7 2.0T FSI fuel flap and manual clearly show these are designed from factory for super. The dealers don't make that clear to the punters as they don't like splashing out for super. So in effect many people are inadvertently de-tuning their cars.

View attachment 61717 View attachment 61718
Sold on 95 RON for my S4 then :)
 

Duggy72

Registered User
Thanks guys. I was surprised to notice that on the filler flap. Tbh I hadn't bothered to look.

It is strange that a 2.0 has 98 as super and the S4 has 95.

If no one has seen any benefits to using super on a std car that means more money for beer lol.

:)
 

GeoffDunk

Registered User
Within the fuel cap, the top figure is the prefered one, this is mine. My car has never had anything in the tank other than Shell V-Power Nitro+ Unleaded.
11655991_868294866598126_1366731106_o.jpg
 

scotty76

Registered User
Interesting the RS4 differs. Thought it was usually forced induction which needs the higher grade which is why the S4 seems an oddity.
 

chucky1

Registered User
Same here. 95 RON recommended. 91 RON 2nd choice in S4s. RS4s, 98 RON with 95 if necessary.
 

xpoweruk

TTTS 8J Smile Machine
Interesting the RS4 differs. Thought it was usually forced induction which needs the higher grade which is why the S4 seems an oddity.
Perhaps it's all to do with keeping the S4 firmly in it's intended slot in the B8 range.
 

Dippy

Registered User
As we know the 3.0 TFSI is quite a capable engine and can easily be tuned to around 480PS. The stock B8s were around 350PS even though they were supposed to make 333PS and that's why Audi reduced the redline in the B8.5 to keep the power down. They needed to ensure there was a significant enough power gap between the S and RS. Maybe the decision to tune to 95RON instead of 98RON was part of this, but I think the reason is simpler: Audi are trying to sell S cars to the general public and not just enthusiasts. My guess is that there are a lot of S car buyers who would be annoyed that their car 'needs' super, especially if its a company car and their policy is 95RON only.
 

GeoffDunk

Registered User

razza1

Registered User
With the remap its tesco 99 all the way...
 

chucky1

Registered User
Tesco is a supermarket yeah? I remember drinking their cider in 2 ltr plastic bottles 30 years ago. Whose fuel do they rebrand? Is it less expensive? I ask this because we haven't gone down this pathway yet.
 

razza1

Registered User
Tesco is a supermarket yeah? I remember drinking their cider in 2 ltr plastic bottles 30 years ago. Whose fuel do they rebrand? Is it less expensive? I ask this because we haven't gone down this pathway yet.
Generally avoid supermarket fuels, but 99 momentum is good, especially if remapped
 

ub7rm

Registered User
My mk5 GTI and 8P S3 had 98 as the recommended fuel type and it was something to do with allowing the engine to operate in the FSI mode more of the time which helped emissions etc though it did also develop more power for better fuel efficiency. I think the latest versions of the GTI / S3 2.0 TFSI engines now recommend 95 rather than 98 as well and presumably thats because the technology has advanced to the stage where then can better control the NOx thats generated as part of the FSI process and this was the reason why it couldn't run in FSI mode all the time.

Presume its the same for the 3.0TFSI in that they've just moved the technology on to allow the same result (emissions) for a lower / cheaper grade of fuel.
 

rum4mo

Registered User
I seem to remember reading that there was a European directive that dictated that after a certain date, all new models of cars coming to the market had to run on "normal" fuel, obviously any car models coming on the market before that time but still being sold were/are not subject to that directive.

What I don't know is if supercars get hit a bit more with taxes and so can continue to get round that directive.
 

GeoffDunk

Registered User
91, 95 & 98 RON fuel and all other sold at common fuel garages are what you call "normal" fuel so there is nothing out of the norm avaialbe.

Supercars are taxed and legislated in exactly the same way every other car is in both the UK and mainland Europe. I pay ovrer £495 a year in road tax because of the emissions which is the same as my mates brand new Range Rover and a friends Gallardo.
 

rum4mo

Registered User
I think that you will find that what I refer to as "normal" fuel are what sells under the description of "UL" as opposed to "UL+".
 

Tfsi gone

Well-Known Member
image.jpg
Out of curiosity I checked my fuel filler cap earlier and this is what's on my 2011 2.0 TFSI.
I always use Shell V-Power Nitro+ by the way...
 

Tfsi gone

Well-Known Member
I thought Super, Premium were a minimum of 98 RON not 95?
Think we've started something now..
May need to get a new sticker lol...
 

GeoffDunk

Registered User
Irrelevant of the name super etc. 95 is 95 etc, go by the numbers. Also, they don’t just print the minimum, mine has both but in reverse, 98 then 95 stating that 98 is the preferred fuel.
 

Dippy

Registered User
My sticker shows 95 & 91. Can you actually find 91 in the UK?
 

Tfsi gone

Well-Known Member
Irrelevant of the name super etc. 95 is 95 etc, go by the numbers. Also, they don’t just print the minimum, mine has both but in reverse, 98 then 95 stating that 98 is the preferred fuel.
image.jpg

I decided to check the vehicles handbook as my fuel filler label only mentioned a min of 95 RON. Strangely the handbook mentions 91 as an emergency measure if there's no other fuel available too.
Doesn't really mention 98 RON & above/Super Plus however like I said I wouldn't use any thing other than Shell V-Power Nitro+
Seems to run the best (quicker and cleaner - exhausts tips stay clean) on that even if it does cost a bit more..
 
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gizze

Registered User
Interesting thread.

I honestly think there is some sort of mistake in the labelling on the B8 S4 in the UK, or Europe.
And since when have we called 95 premium? That is what the US guys call premium.

95 and 91 Ron just doesn't make sense. For a start when was the last time you saw 91 ron in Europe?

In the US they have shown gains of nearly 20hp using 94 vs 91 (we are talking Octane here) and nearly the same using 87 (which is 91 ron).

The B8 does have a knock sensor and it does ****** the timing going from 94 to 91, so why would the UK model be any different?
I just can't see them limiting you to 95 ron fuel, especially as far better detergents go into the premium fuels too.
 

rum4mo

Registered User
I'd reckon that if you went "on tour" on "new Europe" and/or its neighbours, you might just find 91 ron petrol, as I said a lot earlier, there is a directive - or maybe just a "drive" to limit/stop the general demand of 98 ron etc petrol in established/developed Europe, so that translates into new cars "requiring" 91>95 ron petrol.
 

gizze

Registered User
But why in the USA do they recommend 98 ron in the S4, but over here 95? It makes little sense.

Allowing 98 ron will allow advanced timing which not only gives better power but also better mpg, so it makes very little sense to not use what is commonly available, and I just can't see Audi limiting the map which in turn gives poorer official figures.

What other model says 95ron max?
 

gizze

Registered User
I'm not saying I am right by the way, just that it makes no sense to me for Audi not to map their cars for the best fuel and the knock sensors ****** the timing as the fuel gets poorer.

They only have to show figures for the best fuel available, power and mpg, so why would they not allow 98 ron?

With the **** the VAG Group are in currently with regards to doctoring the official MPG/Emissions figures, it just doesn't make any sense for them to not bother allowing 98 ron fuels which can give a good 5-10% better MPG than 95 ron.
 
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