Member Since: 22 Feb 2006
Location: Sunny Cornwall / UK
Posts: 518
Whats in petrol (explained)
This is something different but well worth reading. It was written by our learned friend in Stoke and we think is of interest to any car or bike owner.
Well…………! In The Beginning there was Carbon and Hydrogen.
These got together in accordance with rules forged in the Big Bang (yes, really!) to make methane, one carbon atom with 4 hydrogens stuck on.
A bit later, (only 4000 million years) other atoms started getting together and finally came up with Life, a self-reproducing chemical mix. The reproducing bit was quite fun, but after 600 million years even that gets boring.
So, a more or less intelligent life-form invented The Car and the Motorcycle, the ultimate boredom cure. This was, and is, powered by the Internal Combustion Engine, which must have fuel.
Methane is a fuel, which means it burns in air to produce energy, but unfortunately it’s a gas; a tank-full would propel a Honda 50 for about half a mile.
But! Methane had not been idle since the formation of planet Earth, and had joined up with more carbons and hydrogens to make chains called ‘hydrocarbons’. Well, they weren’t called that at the time. They had to wait for a life-form to evolve that liked giving things names, and a hundred and 20-odd years ago chemists had to learn Latin, so they called the one with five carbons ‘pentane’, the 6-carbon one ‘hexane’, then ‘heptane’ then ….wait for it…. the 8-carbon one ‘octane’ and so on. (If we were naming them now the last one would be called ‘eightane’ so you would need 95 minimum REN for your engine.)
All these things were liquids, very thin and volatile, and pure concentrated energy. The Hildebrand and Wolfmuller (rough 1894 equivalent of the Honda 50) now did 100 miles to the tank full.
Unlike water, these liquids don’t stand around in lakes. They are hidden underground in porous rock so you have to drill for them. The old name was ‘petroleum’ meaning ‘rock oil’ but this was soon shortened to ‘petrol’. The petrol came out of the wells mixed with heavy oil, so it had to be distilled off in an oil refinery.
Early on, the pale coloured stuff that evaporated easily and caught fire very easily was sold as internal combustion engine fuel. It was a simple as that. ‘Octane Number’ hadn’t been invented, but in modern terms this ‘light petroleum fraction’ was about 50 Octane. Now we all know that in the GCSE Science engine The Piston squeezes the air/fuel mixture, then The Spark Plug ignites it to produce The Power Stroke.
The trouble is, with 50 octane fuel if The Piston squeezes too much the heat generated by compression makes the stuff Go Bang prematurely before The Spark Plug gets a look in, giving a Power Stroke with as much push as a fairy’s fart. This is why early engines couldn’t use compression ratios above 4 : 1, and 10BHP per litre was seen as hot stuff.
Engines improved but petrol didn’t and even some time after WW 1 a touring 1000cc engine only turned out about 25BHP, and a hot-shot Sport version with the latest overhead valves would need a good tuner to get 50BHP.
So finally some effort was made to stop primitive petrol going bang too soon, and a variable compression engine was invented for research. (The ‘CFR’ engine, as used for finding Research and Motor Octane Numbers, RON and MON, to this very day.) Early on researchers found that the bung in the CFR head could be really screwed down if a heavy liquid called ‘TEL’ (tetra ethyl lead) was added. This was really effective and cheap, and allowed the ‘straight’ petrol to be upped to 90 or even 100 octane, and a whole load of exciting high-power engines were designed around these fuels.
This leaded fuel survived into the late 1990s, but much earlier an amazing discovery had been made. The shape of the petrol molecules was very important. ‘Octane’ if the ‘straight eight’ version with 8 carbons in a row had an ‘octane number’ of 25. It was only the mutant octane with 5 carbons down the middle and the others sticking out from the sides that gave the best results at high compression. (This special octane is still used as a standard for 100 octane. Proper name is 2,2,4-trimethyl pentane.)
Today, ‘petrol’ is really a synthetic fluid built up from oil industry feedstocks. Very little of it is unmodified distillate from crude oil. It is tailor made to include the best compression-resisting molecules so that no poisonous and polluting lead compounds are needed to reach 95 or even 98 octane. Nothing much is added, apart from a touch of detergent to keep the engine top end clean. Quite a lot of petrol now has 5% ‘renewable’ alcohol as a planet-saving gesture, but this also improves the octane number (by about 1 ) so there’s nothing wrong with that.
Anyway, if you have a motoring holiday instead of flying ComaJet, you are keeping that carbon footprint down….and paying too much tax as well…..but that’s another story.
Fascinating stuff.
Cheers
Guy
20th Feb 2009 2:13 pm
stapldm
Member Since: 11 Sep 2006
Location: Swine Town
Posts: 2330
Excellent info Guy, many thanks.
For those that enjoy some good irony, the inventor of TEL is single handedly responsible for most of the pollution produced in the 20th century, having invented lead in fuel and Ozone depleting CFCs - both considered major advances at the time http://en.wikipedia.org/wiki/Thomas_MidgleyDr. Ian Malcolm:
"Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should."
Transgenic tomato anyone?
20th Feb 2009 3:25 pm
oilman Site Supporter
Member Since: 22 Feb 2006
Location: Sunny Cornwall / UK
Posts: 518
Thanks
Cheers
Guy
20th Feb 2009 5:28 pm
frogall
Member Since: 29 Aug 2008
Location: Norfolk
Posts: 250
Nice.
I enjoyed that.
Now who's going to start on Diesel?
I'm on a whisky diet. I've lost three days already.
Diesel is known in the trade as 'Heavy Oil'. Basically, it is the sludge that collects at the bottom of the tower in the catalytic cracking procedure used (partly) to produce the fuel shown above.
Why it's so expensive is all down to the Labour government The older I get, the more I realise that people confuse wrinkles for wisdom
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20th Feb 2009 9:19 pm
Ken
Member Since: 20 Feb 2006
Location: Here
Posts: 10865
What about LPG its awaste product and we still get charged & taxed on that
20th Feb 2009 9:47 pm
1955diesel
Member Since: 08 Mar 2005
Location: Birmingham England
Posts: 31
[quote="JMC"]
frogall wrote:
Why it's so expensive is all down to the Labour government
The percentage of fuel price due to tax is still around 67% which is the same as the last year of Conservative government according to PetrolPrices.com It was under the Conservatives that the tax went up due to their "fuel price escalator"
22nd Feb 2009 10:38 pm
Tawny Owl
Member Since: 22 Oct 2008
Location: Here and there
Posts: 1645
Just to confuse the issue more, the first automotive fuel in widespread usage in the USA didn't come from crude oil, but from natural gas. It seems that a natural gas pipeline made of wood (held together by iron bands, so it looked like a very long whiskey drum) ran under the Monongahila River, near Pittsburg, Pennsylvania. As the gas flowed flowed through the pipe across the river, it cooled and dropped out the heavy ends (again, think about the cooling coils at the top of an illicit whiskey still). These liquids eventually plugged the pipeline, since the pressure was so low it couldn't shove out a big load of liquids. The solution was to fill a ball made out of pig-skin with water and put it in the pipeline every 2-3 days. This forced the liquids out the downstream end of the pipeline. It was found that these clear hydrocarbon liquids, mixed with a bit of tetra-ethyl lead made for good automotive fuels, except on hot days when they re-vapourized. The name for these liquids was "gas of the line", which was shortened to "gas-o-line" (which you can see in old US movies), further shortened to gasoline, then gas. Nowdays most of the US fuel mix is from crude oil but the name persists.Jim Dowell - D4 HSE TDi, 12,000 hydraulic winch & hidden winch mount, MTRs, TyreDog, Traxide 2 x aux battery system, fixed air compressor, Dolium roof rack, MitchHitch.
RIP 2005 D3 HSE V8 5 seater gold (stolen and torched)
23rd Feb 2009 5:59 am
Roel
Member Since: 16 Aug 2008
Location: home
Posts: 1215
Another name that stays on are the Pigs. Nowaday to clean and inspect pipelines they use state off the art electronic pigs.Roel
1997 Camel Trophy Disco ex-P101JWK (traded it for a Britains 42101)
1984 90 TD5
2005 G4 Disco 3 BN55WPT
Also member of club MTR
and Club Faultmate
Interested in my 4x4 history see my website: www.mudmachine.webklik.nl
Sorry it's in Dutch and with google translator it gets funny.
23rd Feb 2009 8:35 am
ChemicalJasper
Member Since: 19 Jun 2008
Location: Lincolnshire
Posts: 48
JMC wrote:
Diesel is known in the trade as 'Heavy Oil'. Basically, it is the sludge that collects at the bottom of the tower in the catalytic cracking procedure used (partly) to produce the fuel shown above.
Not sure that's entirely true, Diesel is blended out of the general distillate pool from various refining units and is by no means the heaviest component from most crude stock, which would be your bitumens and tars! The UK is a net importer to the distillate pool as we cannot make enough in the UK unlike petrol. The distillates go into the Avtur (aviation fuel) market as well as domestic heating, that along with the short supply situation drives the high price.Don't worry..... it only seems Kinky the first time you do it!
Yes, that's right, the tars and bitumens are at the bottom. Long time since I did Chemistry..... The older I get, the more I realise that people confuse wrinkles for wisdom
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23rd Feb 2009 4:22 pm
Tim in Scotland
Member Since: 27 Jun 2005
Location: All at sea
Posts: 496
I don't think you would want to use Heavy Fuel Oil in your car's engine..................... the fuel pump wouldn't be able to move it as it requires to be heated to something like 60C just to get it to flow. It is very cheap though, which is why most big marine engines run on it............................ it is also very polluting both as a fuel and the emissions! This is the engine that powers my ship and it runs on HFO -
http://www.marinelink.com/Story/W%C3%A4rts...04424.htmlNow a disillusioned new Land Rover buyer and have jumped ship to something less expensive and more reliable that hugs trees.... now driving a Mini Countryman PHEV as well as my trusty and brilliant 1996 Epsom Green Defender90 Tdi300
23rd Feb 2009 5:51 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26704
Thats an impressive motor Tim 8)
From reading the blurb, it sounds like the EGE system is a better idea for efficiency than the EGR
23rd Feb 2009 8:57 pm
SPOTTER
Member Since: 06 Dec 2006
Location: Adrift........
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who will be the first to fit an economiser to their D3?? end of an era ....... maybe a Defender when it appears.......
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For those that enjoy some good irony, the inventor of TEL is single handedly responsible for most of the pollution produced in the 20th century, having invented lead in fuel and Ozone depleting CFCs - both considered major advances at the time 
expensive is all down to the 
Yes, that's right, the tars and bitumens are at the bottom. Long time since I did Chemistry..... 
