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I've just had it pointed out to me that Tesco do a RON 99 fuel which might well go well with the S5. Anyone tried it out on their machine yet?
Any other recommendations for RON 98/99 fuels which work well with the car?

Thanks,
JP
 

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I've just had it pointed out to me that Tesco do a RON 99 fuel which might well go well with the S5. Anyone tried it out on their machine yet?
Any other recommendations for RON 98/99 fuels which work well with the car?
Thanks,
JP
I only use Tesco 99 (T99) in the S5. If I need to fill up and no Tesco is close then I fill up on Shell V Power, but I find that the S5 prefers the T99. Pick up just seems smoother on the T99. I can't tell the differnce performance wise between V Power and T99 but you can if you use the cheap stuff, which I did once when I had to fill up at an ESSO and the best they had was RON 97.
 

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just know that unless your ecu has programming specifically centered around it, running higher octane fuel won't have any actual difference on anything other then your wallet.
 

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Not strictly true RS4, the knock sensors will advance or retard the ignition timings to compensate for lower octane fuel, it's therefore reasonable to notice a slight improvement using 99 octane instead.
 

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just know that unless your ecu has programming specifically centered around it, running higher octane fuel won't have any actual difference on anything other then your wallet.
Just for your reference there have been many independant tests on higher octane fuels to prove if there is a difference or not, here is a link to one of the UKs more repectable tuners with the results from their tests: http://www.thorneymotorsport.co.uk/tuning/Fuel_Test_Results_Update.shtml

Also as blade the freature blade has stated is common in nearly all modern motor cars to compenstate for the fact that some places may only have lower grade fuel.
 

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Here's the theory... The higher the RON (Research Octane Number), the higher the resistance to 'knocking' or pre-ignition under compression. The tendency to 'pre-ignite' also changes with RPM. Therefore higher RON will burn with more accurate timing across the rev range, providing more efficiency and power.

The engine should have no compensation to do as the fuel will burn as the timing has been designed... compensation is only really needed when lower RON fuels are used and the knock sensor adjusts the ignition timing to avoid knock problems.
 

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The engine should have no compensation to do as the fuel will burn as the timing has been designed... compensation is only really needed when lower RON fuels are used and the knock sensor adjusts the ignition timing to avoid knock problems.

Correct, while the ecu will retard the timing for lower octane fuel (when detecting pre-ignition) it will not work the other way around.

The time and expense taken to tune an engine at an octane level unavailable and unknown to the majority of owners makes it a very low priority on a manufacturers list.
 

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i work with scrap yards all over the uk
some say not to use a certain supermaket fuel as they have seen
"many ":eek: :eek: cases where the catalytic converter has been affected so much it needs replacement or at least lamba sensor replacement
so when i get s5 i wont be using that fuel
Only what i have heard,and not in one area of country
 

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Correct, while the ecu will retard the timing for lower octane fuel (when detecting pre-ignition) it will not work the other way around.

The time and expense taken to tune an engine at an octane level unavailable and unknown to the majority of owners makes it a very low priority on a manufacturers list.

It depends entirely on the ECU. It was discussed in some detail on other forums i've been on in the past (Some tuning forums and Alfa Romeo forums). Believe it or not, some ECUs will adapt over time to compensate for the higher 99RON fuel, the ECU in effect, "learns" that the car is using a higher RON fuel, even if it was first programmed to run on 95.

So it can work the other way around if you have the correct ECU and use it for long enough for it to "learn".
 

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...Although (please correct me if I'm wrong) the S5 is nominally designed for 98 RON? (UK Spec S5)... as are most 'performance' engines, due to the higher compression ratios??
 

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Ian, i'd imagine it be 97RON. I've never seen any 98RON pumps about.

It should tell you in your handbook what's recommended? ...It normally does, or even on your petrol cap?
 

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Ah 1 out... I knew I should have looked. Personally I pay little atttention to this stuff and just put BP Ultimate in it. as I get Premier points from BP. ;)
 

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Ah 1 out... I knew I should have looked. Personally I pay little atttention to this stuff and just put BP Ultimate in it. as I get Premier points from BP. ;)

Ditto, the company has an account with BP, so i've got to use their Diesel Ultimate. Hopefully that'll be changing to Shell soon though so I can go back to my V-Power diesel :)
 

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It depends entirely on the ECU. It was discussed in some detail on other forums i've been on in the past (Some tuning forums and Alfa Romeo forums). Believe it or not, some ECUs will adapt over time to compensate for the higher 99RON fuel, the ECU in effect, "learns" that the car is using a higher RON fuel, even if it was first programmed to run on 95.

So it can work the other way around if you have the correct ECU and use it for long enough for it to "learn".
if someone can provide me evidence of a stock, non-altered ecu that compensates for higher then premium octane fuel then i will be impressed. Until then, I stand buy my statement that it's a waste of money.
 

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Well on the S5 on the fuel filler cover it says min RON 95 and normal RON 98. Therefore as we have RON 97 and RON 99, I would assume then that 99 should be used as the norm then as we don't have 98 RON fuel.

For me personally though, i think of my car as I would my the human body, good food = good performance so good fuel = good performance too. :)
 

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if someone can provide me evidence of a stock, non-altered ecu that compensates for higher then premium octane fuel then i will be impressed. Until then, I stand buy my statement that it's a waste of money.
Here you go: Independant test, with dyno results to prove that higher RON fuel makes a difference, in both an old unmodified MR2 and an M3 CSL.

http://www.thorneymotorsport.co.uk/tuning/Fuel_Test_Results.shtml

This is a link to the full pdf report: http://www.thorneymotorsport.co.uk/content/site/downloads/press-release-full-290806.pdf as I noticed the links to the dyno results aren't working however they are in the pdf.

As for those that can't be bothered to read the report the conclusion is as folows -

"It is clear from the testing that whilst older engines show a clear benefit of running higher octane fuel, 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 Octane fuel was over 40bhp, that’s over 10%.

It is our fundamental belief and now our clear recommendation to our customers that if they want to maximize the power of their cars, before they even consider using our services to enhance the power of their car further, they should use the best fuel they can buy. The simple fact borne out of our extensive test is that using Tesco 99 Octane fuel will make your car more powerful. It will feel faster, accelerate faster and perform better. If you’re going to tune your car at least give it the best fuel it can run on and in our opinion, based on extensive testing that fuel is Tesco 99 Octane."
 

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Any differance between uk Ron 99-and US 99 octane????
 
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