Dan, it will be interesting to see what they come back with.
I can deffo confirm that my previous STI v3 ran MUCH better on Maxol E5, as did my WRX SL and my MINI JCW, that said, might still be only 97RON.
Definitely Applegreen is only RON95 (at best) and no better than anything you can get at branded forecourts.
Pablo, (bio)ethanol is about 108.5RON, so to calculate mathematically: (95*95)+(5*108.5)=9567/100= RON95.6
-- however, it's not quite that simple as apparently the chemical properties mean results aren't 100% linear.
e.g. NF booster full bottle on a tank should give you +3 or +6 on a full tank (Red or Black bottle), however, putting in a half bottle will give you more than +1.5 or +3, and putting in two bottle does NOT give you +6 or +12.
Another big influencer is the stock fuel you started with: e.g. if you start with RON92 then NF booster will give you close to +4 or +7 on a tank, but start with RON98 and you will only see about +1.5 or +3.5 hike in RON.
Legally all fuel should meet the minimum RON95 standard in Europe, including Ireland. As we all know, fuel can go "stale" and lose RON when it's sitting around too long. This is factored in to some extend by suppliers (well the reputable ones like Maxol, Texaco, Topaz, ESSO, etc). Hence very fresh fuel will typically be in the range of RON95.2-95.6 depending on brand, which will deteriorate over time. If left long enough it will go down by several points. Then of course there are contaminants (old tanks leaking water, changing fuel types in tanks or transporters etc) which can further reduce RON ratings.
Given the above the BEST pump fuel you will get will probably be from a BIG forecourt of a REPUTABLE brand in a BUSY location.
Reason being: it starts out with the best margin, it is brought by their own tankers which only carry one fuel type in a designated tank (no changing of fuel types depending on where they are delivering what), less chance of ever changing fuel type in the forecourt storage tanks, sell a lot of fuel all of the time so little chance of fuel sitting long enough to go stale.
BTW, the above also applies to Maxol of course... they start with arguable the best RON rating in Ireland and factoring the extra margin built in for aging fuel, is why we probably see it perform near RON97 levels.
Keep in mind that the caloric value of fuel also influences MPG if anyone is wondering why you get less MPG out of Applegreen -- bio diesel (rapeseed based), bio ethanol and LPG have lower caloric values than normal diesel or petrol. Hence you need more of it to generate the same amount of energy (to move your car) and hence MPG will always be slightly worse with those fuels regardless of improved RON benefits (compared on same engine with tune for that fuel).
As stated before though... be careful about some forecourt owners getting cheap fuel from a different brand and retailing under the guise of brand A, but selling cheap brand X stuff.
Wagon Dec is on the money: Seeing that most stations at best supply RON95 is it worth tuning for, at best, RON97 with all the hassle for trying to get it and all the risk of getting a dodgy batch that is lower and does damage? I just got mine tuned for RON95 for convenience and peace of mind - and you know what... power is so good there's little in the difference to tune for another 1-2 RON.
