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I should be picking up my new fn2 type r today and I was just wondering what fuel to use? In my subaru it was a MUST that I used either tesco momentum or shell vpower. It would not run on anything under 99. Am I ok using 95 or better sticking to 99. Not sure what these cars like so any input welcome. Thanks, stu
 

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95 will be fine. Stoney gave an explanation of why 99 makes no difference iirc?

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In very simple terms: On a boosted engine (turbo or supercharged) the heat of compression makes the fuel more like to detonate rather than burn smoothly. This means you either have to retard the ignition (which helps reduce this effect but also loses power) or use a higher octane fuel which is much more resistant to detonation in the first place. If your Subaru was previously mapped to run on 99 octane, sticking 95 octane in would means lots of det and an early death for the engine...

On a non-boosted (ie NA engine), the fuel/air mixed is much less 'stressed', which means detonation is less likely to occur, meaning that standard 95 octane can be used without the need to retard ignition. The exception to this are NA engines running high compression - the higher compression stress the fuel/air mix more, which means det can be a problem unless a higher octane fuel is used.
 

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The stock map is for 95

The ECU cannot advance timing automatically to make benefit of any superior fuel


The rest is your choice
 

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I use V-Power/BP Ultimate purely for the cleaning properties...the extra £3 or so per tank is no skin of my nose for a cleaner engine :)
 
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