JCW 'S' Fuel Question

[duncs]

This has probably been covered in some thread somewhere, although I couldn't find it.
I have seen a lot of references around as to how good Shell Optimax is.
I thought this was 98 Octane fuel, and from memory I thought that JCW tell you to use 95 to 97 Octane.
I use Super Unleaded ( 97 Octane ) at the moment, can I use the Optimax or is it to higher Octane level.
Or have I misread or misunderstood something?

If I can use it, any comments / reports on the differences to super?.

[Tall bloke]

I only ever use Optimax in my works s. Can't really give you a comparison, because i have never filled up with anything else (even before the conversion).

Chris

[duncs]

I assume, having never used anything else that you have had no problems?.
Provided I can't find any negative comments, I will give it a go.
As opposed to you I have never used it.

[Tall bloke]

I have put 18000 miles on my car in a year, and can count on one hand the amount of times i have used petrol other than Optimax. I have had no problems what so ever.

Cheers
Chris

[duncs]

Thanks Mate
Will give it a go.

[davidac]

I know the numbers don't convert directlyto US, or at least I think I know. What is the conversion approximately. 98 octane in the UK is equivelant to what in the US? The hightest octane widely available is anywhere from 92-94 depending ont he station here, but I think those numbers are calculated differently. I am sure someone knows, care to explain?

[duncs]

As far as I was aware, the octane rating was a standard number wherever you were.
I thought basically, the higher the octane rating the less likely the fuel was to pre-ignite ( due to compression and not the spark ), i.e. reducing effiency.

I know that in high altitude countries you tend to get lower octane rating fuel, I guess this is something to do with available oxygen.

I know that in south africa around in Gauteng ( approx 2000m above sea level ) that most Garages supply 93 or 95 octane fuel.
If I remember in Cape Town ( sea level ) you can get 97 octane.

Here in the UK, it ranges from 93 to 97 ( typically ) Optimax is 98.

I know this probably doesn't answer your question, I'm hoping there is a budding Chemist out there who may be able to tell me I am talking rubbish and explain the process properly.

[d2create]

In the US, most gas stations offer three grades. 87, 89, and 93. In California i believe it's very hard to find anything over 91 due to stricter emissions.
So for the US, what octane does the S call for?

[Critical]

Ok, the octane ratings in europe and the US are the same. They are the ability of the fuel to withstand compression-induced ignitions. The higher the octane rating, the more it can be compressed before it will ignite. High performance engines require higher octane fuels because they compress the fuel more before they ignite it (spark). If you put low octane gas in a high compression engine it will ignite pre-maturely - pinging. The octane rating is the rating of the compression window of the fuel referenced against pure mixtures of heptane and octane. So a 93 octane gas will give the same window as a mix of 93% octane (a poor igniter) and 7% heptane (a good igniter) - this does not change depending on your continent. Altitude would affect this, but im sure the ratings are referecenced at sea level. As for how they get >100 octane fuels....you got me (probably some extrapolated value)??

[davidac]

I did know that higher octane gas is more stable and has less of a tendancy to ignite under pressure. I belive that is what is known as knock. The explosion occuring before the spark plug fires that is. I was refering to the method of calculation. In the US it is R+M/2 but I think there is also a method called RON and also MON, not that I know what any of them mean. I just know they come up with a different numerical value for the same gas. But if the European method is the same as the US method and you all are running 98 and the best I can get here is 93 no fair.

[d2create]

Quote: Originally Posted by davidac

But if the European method is the same as the US method and you all are running 98 and the best I can get here is 93 no fair.

And all this time I thought it was outrageous that gas was so expensive in europe. Now I know why!
In the US we call that stuff 'race gas' and it costs $5 per gallon here too.

[KatanaPilot]

Quote: Originally Posted by davidac

I did know that higher octane gas is more stable and has less of a tendancy to ignite under pressure. I belive that is what is known as knock. The explosion occuring before the spark plug fires that is. I was refering to the method of calculation. In the US it is R+M/2 but I think there is also a method called RON and also MON, not that I know what any of them mean. I just know they come up with a different numerical value for the same gas. But if the European method is the same as the US method and you all are running 98 and the best I can get here is 93 no fair.

Hi everyone,

the Octane rating in the US (and Canada) is different from the Octane rating used everywhere else in the world.
As davidac said, in the US and Canada it is R+M/2. The rest of the world just uses the higher one (RON I think). A 93 in the US is probably equal to 97 or 98 elsewhere. I also found that I got slightly better gas mileage using Shell gas.

[EBMCS03]

there are three Octane rating systems, RON, MON, and AKI which is (RON+MON)/2 with MON < AKI < RON.
Here in the US we use AKI and in Europe I've mostly seen RON. Any country use MON ?

For example, BMW recommends for it's K1100 motorcycle: a minimum of 89 AKI, 95 RON, 85 MON.

The MCS I THINK recommends a minimum of 91 AKI which doesnt matter to me cuz thats what i use for all my cars anyways... I drive pretty close to redline a lot of the times and I can use that extra insurance...

[bigbaddaboom]

Here is an interesting article on 100 octane fuel, RON, MON and AKI:

http://www.leesracing.com/articles/a3.html

[Nic D]

There might be a 100octane rated Shell V Power fuel out soon too, and BP are considering rolling out the same octance level.

I never ever ever use UL and stick to Optimax except where forced to use SUL.