nom

I've just been pondering.
Overall, I've found that on a strictly 'performance' basis (as in ignoring the cleaning blah blah blah properties that it's meant to have), Optimax seems to behave pretty much the same as, eg., Esso SUL - it feels similar, possibly a little better - and I log the occassional 1-2 degree retard - about normal, AFAIK, on both fuels.

Yesterday, in the morning I had a tank of the Esso 97RON, then filled up later with Esso 98RON. A whopper of a difference. I reset the ECU before both fill-ups to keep things as similar as possible - zero knock correction over a couple of hours of all sorts of traffic with the 98 stuff. I was also getting 16.4psi sustained boost rather than around 15.1 (that's measured coming in & going out of the petrol station, so conditions were identical!). That's Tek2 provided boost, BTW.

So if that's what it's like with 98 RON (real official stuff 'cos it says so on the pump ), why does the 'official' (although not advertised as such) 98.6 RON of Optimax seem to behave as it does? As in like a 97 RON?

Have a ponder. I may well be getting entirely the wrong end of the stick here, but I thought that a fairly clear indication of 'effective' octane rating would be how much knock correction is needed. If so, what's it with this Optimax, then?

Razor2001

Nom you got a JDM spec ?

Trout...

Esso don't do 98RON fuel. The have old stickers on pumps.

Optimax has an improved RON over other fuels

A test by ITS/FIA (admittedly paid for by an Octane Booster company) gave Optimax a 98.3 RON rating up from 96.1 for Shell Premium, the MON rating was 86.9 up from 85.0 for Shell premium.

In my personal experience the car has been optimised for Optimax and if I use any other fuel - then it is knock, knock, knock. On average Optimax has give me just over a degree of advance in high boost areas.

Trout

nom

This really was the 98RON stuff - they still do it in Belgium, along with something called '99+' in some places.
Oh well, maybe Esso fuel is just better than Shell

And I'm not too sure what JDM spec is...

john banks

JDM = Japanese Domestic market.

With a Tek 2 I would not expect a significant difference in knock correction between fuels. Reason I say this is that the Tek 2 map for safety is not running on Knock correction all the time across the range, it is just little bits that peep through and get corrected. These on many cars are so sporadic it is difficult to comment on their relative frequency between fuels unless there is a stunning difference.

I have noticed that with Shell SUL (best grade up here) and 1ml/L NF octane booster I get no knock correction whatsoever despite 20 PSI and between 2 and 6 degrees extra advance over Tek 2 and a fair bit leaner. I don't want to have a car running on correction all the time until I see what happens on the track with it.

nom

There was a fairly stunning difference - I'm used to seeing a little jiggling of the knock correction line, at most to -2, and that not very frequently. However, this time round, there was nothing over about 2 hours - much the same as you manage to get with octane booster. Which I thought was quite good. The car felt sooo much better on it too! Almost like changing from NUL to SUL again, which Optimax certainly doesnt do - it's a much more subtle change than that.

mutant_matt

Nom,

Esso don't sell 98RON in this country, but I'm sure they do on the continent. I have to say that Optimax felt noticably better than Esso Super in my MY00 which felt noticably better than any other SUL and NUL.....

Matt

BoxerFlat4

Has anybody here with a EGT gauge measured any differences between normal SUL and Optimax ? Reason I ask, a couple of my customers have mentioned that with Optimax, exhaust gas temp. goes up through the roof, which was why they'd stopped using it.

Just wondered....

nom

Hmm, wierd stuff with the EGTs!
Matt - I probably should have said a lot earlier - it was in Belgium that I filled up with the 98, which is why I thought it might be 'of more interest' to people as we (as in UK) can't get anything of the 98 type except for (I'm still not convinced) Optimax, and in areas where 98 is usual, they get different Optimax. Which, in itself, look a little suspicious to me . So I could do a direct 97 to 98 comparison, rather than a 97 to Optimax comparison like has been done to death, and I found the 97 to 98 difference to be much greater than the 97 to Optimax one. Which it shouldn't have been.