98 vs 100 octane

[MR22ZZ]

no it's not, it's a measure of ignition retardation of the fuel.
If it were a ratio, how then is there 102, 105, 108 RON fuels?

[AdrianS]

I agree with the majority of posters here - there is probably SFA difference running 98 vs 100. I am not chasing max possible power, and I'm sure it will run ok.
I just wondered if anyone had hard data on the effect of different octane ratings on a motor designed & tuned for 100 RON. I know that if a n/a ECU is designed/tuned for a specific octane fuel, higher octane won't help.
When time / money permits, I will do some dyno testing and post results. (But don't hold your breath).

[oldcorollas]

Not every servo in Japan has 100 RON fuel. The engine/ECU would have been designed with this in mind, ie maximum performance with 100 RON but still runs OK with lesser fuels.

I have never seen or heard of a servo here that does not have "Hi-Oc". It is such a standard fuel for so many vehicles (anything with high conpression or turbo) that it wouyld be difficult to find somewhere without it... maybe on the outlying islands or very far in the country (if there is such a thing?)

octane number is a ratio, nothing more.

it is a ratio, but it means the "ratio of detonation resistance, compared to n-heptane and iso-octane.

read here, RON, MON and PON(=[MON+RON]/2) explained
and here

Adrian, the NA cars will have some leeway as the timing is not tuned to ragged edge, and are often a bit rich stock. maybe just be careful when temps are high...
Turbo cars may have more problem, but probably not at stock boost levels (unless it is one of those WRX's )

edit: if anything, you will find that you are closer to edge with 98 than 100, but also that you have a little more room to up power/tuning with 100.. since stock tuning is dumbed down a bit for the masses..

[trdee]

no it's not, it's a measure of ignition retardation of the fuel.
If it were a ratio, how then is there 102, 105, 108 RON fuels?

you can have ratios greater than 100:1

as OC said, its supposed to represent the detonation resistance of fuel, expressed as a ratio between iso-octane and heptane

[MR22ZZ]

i see

cool, thanks.

[eeeyan]

Considering you cant get 100RON off the pump isnt the point kinda moot anyhow? I know you want to know if theres a difference but is it worth the time and effort and money of dyno tuning just to say "there is a difference" when you dont really have much choice at the moment anyhow? short of octane boosters and high octane racing fuels which is an expense i wouldnt want every fill cant you just do what most do and go for 98Ron and jsut deal with it? and if your REALLY fussy get the aftermarket ecu and tune specifically for that fuel. For satisfying curiosity it seems like a waste of time. Just my humble opinion

[AdrianS]

Considering you cant get 100RON off the pump isnt the point kinda moot anyhow? .... For satisfying curiosity it seems like a waste of time. Just my humble opinion

You are right, it's not worth it just for curiosity. But, since it's going on a dyno at some stage to see what power it's getting and check timing / afr, I'd like to do a couple of runs with higher octane and see what difference it makes, if any.

[Celica RA45]

you can buy 100 octane from service stations and there are only a few in melb that sell it .its from united and its called united 100 and its about 1.35 and has 10 % ethenol with 98 octane for the mix there are 2 in croydon and 1 near the sandown race way and 1 at point cook and 1 also up at albury

[eeeyan]

just to note i'm in perth and we take about 100 years to get anything here that u guys have over there.

Cant even get E10 fuel here yet i dont think. How many servo's have that there now?

[oldcorollas]

just a note..
10% ethanol 100octane is not the same as "proper" 100 octane..

[Celica RA45]

shell 100 V power racing was 5 % ethanol

[RONA]

shell 100 V power racing was 5 % ethanol

Which is irrelevant when they don't sell it anymore.

[Celica RA45]

which was bad, but did dyno tests and the united is only 2 kws down on the V power racing and about 8kws down on the ELF race fuel lms which is 100 octane with 3.5 % oxygen

also to note tried E 85 and also some 105 race fuels as well ,with the elf being the very best at power and at price as well 8bucks a litre

[eeeyan]

$8/litre? you would want to be dedicated to use that stuff. I'll stick to Ultimate 98 BP fuel and have money for a beer at the pub after a days driving thanks. When fuel costs mroe than beer your in trouble i reckon.

[andrew_mx83]

united on dorset rd bayswater have E10 100RON. i love it.


and there is a difference between 98 and 100, my old high-comp 7m would run like shit and ping its head off on everything but the united 100RON unless i used a booster (bp ultimate, mobil 8000, v-power, vortex etc all no good)
united fuel gave more power less ping and noticably better economy