From Crude To The Pump
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This is an old document I found knocking about the internet so take some of the numbers they quote whit thet age of the document in mind

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Or for us simpletons, a picture of distillation.

Edited by Oli on 28th Dec, 2009.

Yeh, like 'simple' for kids

The pic does not tell you that gasoline straight off the cracker is around 70 octane nor does it tell you about cat cracking. But then if all you want to know is the kids simple version then I suppose the picture will do, lol.

I work in and around oil refineries. I just have a natural curiosity that the picture above cannot satisfy

Not that I am putting the picture down, its just a bit simple thats all

Edited by Sprocket on 29th Dec, 2009.

I'll be honest and say i didn't actually think theres was that much more to it, if you know what i mean.

But now i think im going to have to read the link properly.

So, If raw petrol from the distillation column has a RON of about 75, then is subjected to catalytic reforming..... and this causes it to have a higher octane number, does this mean during the reforming it re-arranges the hydrocarbon molecules or breaks them into smaller molercules? Meaning they're differnt shapes...

the way I understand it is that cat cracking increases the yeild, rather than changing its molecular state. Basicaly taking 'other' hydrocarbons, slpits them and reforms them into gasoline, thus increasing the gasoline yeild, but it still has a relatively low octane. The increase in octane comes from the various 'extras' they add, and from what I have read, it varies from refinerly to refinery and manufacturer to manufacturer as to how they get to 95 octane or any other.

One thing is clear though from experience, is that Shell pump fuels have a strong odour compared to the likes of ESSO. Perhaps the difference in the base fuels octane boosters?

What I found interesting was that Butane is used as an octane booster, and apparently the reason why your fuel tank releases gasses when you remove the cap. Butane is a gas, how do they keep it in solution at atmospheric pressure and temperature?

Good point there.

If your fuel tank releases gasses when you remove the cap, would that be the butane evaporating as it has a boiling point of something like -0.5 degrees centigrade?

It could be that the butane gas is disolved in the solution, a bit like the CO2 in fizzy drinks, and with its relatively low staurated pressure will gas off slower than the likes of CO2. This could also account for modern fuels having a very short life span before it degrades?

We are never going to find the exact coctail that makes up pump fuels but understanding what can be used to make it, you then begin to understand people saying pump fuels are only realy good for maybe up to two to three weeks before they start going off.

Edited by Sprocket on 29th Dec, 2009.

the smell of shell fuels is very particular. to the point where my partner at the time, asked me to stop using it in the mini as she hated teh smell.. one of the reasons the mini is tuned on bp 97 ron lol i put the fuel going "off" thing down to additives with a lower boiling point than the base fuel boiling off, but always assumed they would be other liquids, alcohols and the like. never thought it could be gaseous.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.