Help me learn more about petrol
Discussion
I don't mean whether Brand X is better than Supermarket Y, or whether I need to run my 1.0 NA Corsa on 102 RON race fuel or any of that. In fact, one thing that struck me as I've been trying to learn more about fuels in general is that half the internet appears to be driving a (very) broken vehicle. "The minute I filled up at the supermarket my engine light came on and the car drove like a bag of spanners.", "It smokes a lot and idles roughly on fuel A, so you should only ever use B." and so on. It's actually hilarious how many people spout plain incorrect information as gospel ("V-Power is 97 RON mate, but if you buy BP from Sainsbury's it's 98. Don't go to Morrison's though because their fuels aren't British standard...").
I have been spending a few nights on Google trying to find out more about the constituents of fuels and their effects, primarily petrol. For example density (KG/M3 at 15oC), aromatics, and olefins. I have been through Google Scholar and picked up from a Chinese paper that higher aromatics usually lead to less exhaust emissions, but apart from that it's hard to find much else aside from people speculating wildly on forums or generic articles repeating the same old rubbish. It's surprisingly difficult to find out much of anything concrete, especially in the UK. Unlike in the USA - where fuel companies fall over themselves to provide lots of technical data and information about the base stock and additives etc - the UK seems to be under a blanket of corporate silence and absolutely everything is a 'trade secret' leaving drivers to just pay their money and make their choice. Hit and hope, really. One man's tuner insists Momentum 99 is amazing and better for turbos due to the high oxygenates content, while another says it dets like crazy and you should only use 'insert brand here'. You only need 95/97/99/whatever. It's quite silly.
So with that in mind, I have a few quick questions... probably with not so quick answers. Sorry about that. As I said, I'm not particularly interested in sparking a Brand A versus Brand B thread (again - yawn), but my search for what would run best in my car did spark an intellectual pursuit for some deeper knowledge on how it all works.
1) I am aware of the minimum density for petrol as listed in the British Standard, but if Fuel A has significantly higher density than Fuel B, does that indicate higher calorific density too, or anything else that would impact on power and/or economy? Or is it totally unrelated?
2) If fuel A has significantly higher aromatics (and/or olefins) than Fuel B how does this impact the power and economy?
Anything else interesting you care to share that isn't 'from your mate's dad who worked at the fuel terminal all his life until he knew too much and they buried him alive at sea.'...? I'm interested especially in these two fuels, or at least they're the two that set me searching and it's hard to find info on any others. Let's assume they have the same RON and that these are the primary differences:
Fuel A
MON - 86
Ethanol - 5%
Density at 15oC - 741 KG/M3
Olefins - 15
Aromatics - 34.5
Fuel B
MON - 87.3
Ethanol - 5%
Density at 15oC - 760.3 KG/M3
Olefins - 8.3
Aromatics - 35
As you can see, Fuel B has half the olefins but a higher MON and quite a lot more density compared with Fuel A. Don't get me wrong, I use both these fuels (and others) and in the real world I don't notice much difference. One certainly doesn't cause bad running, smoke or ejected conrods compared to the other.
I'm just curious to learn more about fuel in general as I said, and would be interested in learning from anyone who (really) knows more than I do and would be willing to spend a few minutes sharing some knowledge. It's an old habit from university, but I strongly dislike having two sets of figures and being unable to inform myself as to what they mean! I'm fully aware that there's a lot more to a fuel's make up than the few specs I listed, but those are the bits I'm not so sure on. Cheers. 
I have been spending a few nights on Google trying to find out more about the constituents of fuels and their effects, primarily petrol. For example density (KG/M3 at 15oC), aromatics, and olefins. I have been through Google Scholar and picked up from a Chinese paper that higher aromatics usually lead to less exhaust emissions, but apart from that it's hard to find much else aside from people speculating wildly on forums or generic articles repeating the same old rubbish. It's surprisingly difficult to find out much of anything concrete, especially in the UK. Unlike in the USA - where fuel companies fall over themselves to provide lots of technical data and information about the base stock and additives etc - the UK seems to be under a blanket of corporate silence and absolutely everything is a 'trade secret' leaving drivers to just pay their money and make their choice. Hit and hope, really. One man's tuner insists Momentum 99 is amazing and better for turbos due to the high oxygenates content, while another says it dets like crazy and you should only use 'insert brand here'. You only need 95/97/99/whatever. It's quite silly.
So with that in mind, I have a few quick questions... probably with not so quick answers. Sorry about that. As I said, I'm not particularly interested in sparking a Brand A versus Brand B thread (again - yawn), but my search for what would run best in my car did spark an intellectual pursuit for some deeper knowledge on how it all works.
1) I am aware of the minimum density for petrol as listed in the British Standard, but if Fuel A has significantly higher density than Fuel B, does that indicate higher calorific density too, or anything else that would impact on power and/or economy? Or is it totally unrelated?
2) If fuel A has significantly higher aromatics (and/or olefins) than Fuel B how does this impact the power and economy?
Anything else interesting you care to share that isn't 'from your mate's dad who worked at the fuel terminal all his life until he knew too much and they buried him alive at sea.'...? I'm interested especially in these two fuels, or at least they're the two that set me searching and it's hard to find info on any others. Let's assume they have the same RON and that these are the primary differences:
Fuel A
MON - 86
Ethanol - 5%
Density at 15oC - 741 KG/M3
Olefins - 15
Aromatics - 34.5
Fuel B
MON - 87.3
Ethanol - 5%
Density at 15oC - 760.3 KG/M3
Olefins - 8.3
Aromatics - 35
As you can see, Fuel B has half the olefins but a higher MON and quite a lot more density compared with Fuel A. Don't get me wrong, I use both these fuels (and others) and in the real world I don't notice much difference. One certainly doesn't cause bad running, smoke or ejected conrods compared to the other.
I'm just curious to learn more about fuel in general as I said, and would be interested in learning from anyone who (really) knows more than I do and would be willing to spend a few minutes sharing some knowledge. It's an old habit from university, but I strongly dislike having two sets of figures and being unable to inform myself as to what they mean! I'm fully aware that there's a lot more to a fuel's make up than the few specs I listed, but those are the bits I'm not so sure on. Cheers. 8bit said:
I can't help you I'm afraid but I applaud your thread for not being yet another "what car" or "how best to get a <insert boring German car here> on a £299 lease" job.
Also always interested to expand my knowledge so subscribing for updates
Thanks. Looks like we'll be in for a long wait, though... Also always interested to expand my knowledge so subscribing for updates
I can't help you either, but I'm interested to learn more if anyone can.
Thread bookmarked. Interesting thread, OP. Hope someone wiser than me can shed some light on it!
EDIT: I know a decent smattering of A-level organic chemistry and a fair bit of biochemistry, but not the bits that can help the OP.
Thread bookmarked. Interesting thread, OP. Hope someone wiser than me can shed some light on it!
EDIT: I know a decent smattering of A-level organic chemistry and a fair bit of biochemistry, but not the bits that can help the OP.
Edited by blearyeyedboy on Tuesday 5th July 23:09
How good is your chemistry? I can help with this but not if you already have a BSc in the subject.
There is a loose relationship between density and energy content, all other things being equal, bear in mind winter fuel is less dense to help volatility and ignition, and waterfall it's a blend. Some use butane, some not, and aromatics help raise octane.
There is a loose relationship between density and energy content, all other things being equal, bear in mind winter fuel is less dense to help volatility and ignition, and waterfall it's a blend. Some use butane, some not, and aromatics help raise octane.
battered said:
How good is your chemistry? I can help with this but not if you already have a BSc in the subject.
There is a loose relationship between density and energy content, all other things being equal, bear in mind winter fuel is less dense to help volatility and ignition, and waterfall it's a blend. Some use butane, some not, and aromatics help raise octane.
My degree isn't chemistry related (it was psychology with some pharmacology), and I left high school aged 12 for a series of serious operations. So assume I'm intelligent enough but only have a broad overview of the topic. I'm all ears for as much as you care to share! There is a loose relationship between density and energy content, all other things being equal, bear in mind winter fuel is less dense to help volatility and ignition, and waterfall it's a blend. Some use butane, some not, and aromatics help raise octane.
OK brief intro. Fuel is principally hydrocarbons. These are classified by number of carbon atoms. Starting with 1 and going up, for saturated linear HCs you have methane-ethane-propane-butane-pentane-hexane-heptane-octane-nonane-decane (etc).
These are all characterised by a chemical formula CH3-CH2-CH2-CH2 (etc)-CH3. The energy yield is simply calculated by counting the C-C bonds (which have a set energy content) and C-H (likewise) and multiplying them up.
Methane,ethane, propane won't go in liquid fuels as they evaporate too quickly. Butane will stay in fuel for a period, it helps with the volatility of the mixture, exp in winter. Low energy yield though.
As the chains get longer the energy yield per gram invreases because C-C bonds are stronger than C-H. You will find this in a chemistry data book, look up d-H combustion (as in delta H combustion).
Unsaturated hydrocarbons (those with double bonds) have more energy per g. Triples hotter still. That's why acetylene (proper name ethyne, meaning CH-triple bond-CH) burns so bloody hot and is so good for welding. Also why it needs pure oxygen to burn clean.
Aromatic hydrocarbons (with rings, eg benzene) are very energy dense, less volatile than linear HCs of the same C-chain length, and reduce knocking (not entirely sure why, prob less volatility).
Fuel is a mixture of all these things, it varies as to what's available and the manufacturer and season. They aren't too precious about it, and of course if there is heavy demand for certain fractions for industrial processes then they will separate these and throw in more of the crap that nobody much wants. It's only fuel.
Helpful?
These are all characterised by a chemical formula CH3-CH2-CH2-CH2 (etc)-CH3. The energy yield is simply calculated by counting the C-C bonds (which have a set energy content) and C-H (likewise) and multiplying them up.
Methane,ethane, propane won't go in liquid fuels as they evaporate too quickly. Butane will stay in fuel for a period, it helps with the volatility of the mixture, exp in winter. Low energy yield though.
As the chains get longer the energy yield per gram invreases because C-C bonds are stronger than C-H. You will find this in a chemistry data book, look up d-H combustion (as in delta H combustion).
Unsaturated hydrocarbons (those with double bonds) have more energy per g. Triples hotter still. That's why acetylene (proper name ethyne, meaning CH-triple bond-CH) burns so bloody hot and is so good for welding. Also why it needs pure oxygen to burn clean.
Aromatic hydrocarbons (with rings, eg benzene) are very energy dense, less volatile than linear HCs of the same C-chain length, and reduce knocking (not entirely sure why, prob less volatility).
Fuel is a mixture of all these things, it varies as to what's available and the manufacturer and season. They aren't too precious about it, and of course if there is heavy demand for certain fractions for industrial processes then they will separate these and throw in more of the crap that nobody much wants. It's only fuel.
Helpful?
battered said:
OK brief intro. Fuel is principally hydrocarbons. These are classified by number of carbon atoms. Starting with 1 and going up, for saturated linear HCs you have methane-ethane-propane-butane-pentane-hexane-heptane-octane-nonane-decane (etc).
These are all characterised by a chemical formula CH3-CH2-CH2-CH2 (etc)-CH3. The energy yield is simply calculated by counting the C-C bonds (which have a set energy content) and C-H (likewise) and multiplying them up.
Methane,ethane, propane won't go in liquid fuels as they evaporate too quickly. Butane will stay in fuel for a period, it helps with the volatility of the mixture, exp in winter. Low energy yield though.
As the chains get longer the energy yield per gram invreases because C-C bonds are stronger than C-H. You will find this in a chemistry data book, look up d-H combustion (as in delta H combustion).
Unsaturated hydrocarbons (those with double bonds) have more energy per g. Triples hotter still. That's why acetylene (proper name ethyne, meaning CH-triple bond-CH) burns so bloody hot and is so good for welding. Also why it needs pure oxygen to burn clean.
Aromatic hydrocarbons (with rings, eg benzene) are very energy dense, less volatile than linear HCs of the same C-chain length, and reduce knocking (not entirely sure why, prob less volatility).
Fuel is a mixture of all these things, it varies as to what's available and the manufacturer and season. They aren't too precious about it, and of course if there is heavy demand for certain fractions for industrial processes then they will separate these and throw in more of the crap that nobody much wants. It's only fuel.
Helpful?
That's great, thanks very much! I really appreciate you taking the time to type that out. Just one question (as I can now pretty much fill in the gaps everywhere else) - what do the olefins do? Out of the two fuels above the levels are very different, but the fuels perform similarly. You probably already guessed Fuel A is V-Power (I found a Shell UK data sheet after much searching) and Fuel B is Tesco Momentum 99. Since the latter relies more on alcohols (other than ethanol) I suppose that accounts for the extra MON, but is that the reason for the difference in olefins? I'm hypothesising that olefins are petroleum based and that's why V-Power has more compared to the alcohol-rich Momentum? As I said it doesn't seem to affect anything in the real world, if anything my car goes a bit better on the Greenergy/Tesco stuff. Just idly curious. These are all characterised by a chemical formula CH3-CH2-CH2-CH2 (etc)-CH3. The energy yield is simply calculated by counting the C-C bonds (which have a set energy content) and C-H (likewise) and multiplying them up.
Methane,ethane, propane won't go in liquid fuels as they evaporate too quickly. Butane will stay in fuel for a period, it helps with the volatility of the mixture, exp in winter. Low energy yield though.
As the chains get longer the energy yield per gram invreases because C-C bonds are stronger than C-H. You will find this in a chemistry data book, look up d-H combustion (as in delta H combustion).
Unsaturated hydrocarbons (those with double bonds) have more energy per g. Triples hotter still. That's why acetylene (proper name ethyne, meaning CH-triple bond-CH) burns so bloody hot and is so good for welding. Also why it needs pure oxygen to burn clean.
Aromatic hydrocarbons (with rings, eg benzene) are very energy dense, less volatile than linear HCs of the same C-chain length, and reduce knocking (not entirely sure why, prob less volatility).
Fuel is a mixture of all these things, it varies as to what's available and the manufacturer and season. They aren't too precious about it, and of course if there is heavy demand for certain fractions for industrial processes then they will separate these and throw in more of the crap that nobody much wants. It's only fuel.
Helpful?
rainmakerraw said:
That's great, thanks very much! I really appreciate you taking the time to type that out. Just one question (as I can now pretty much fill in the gaps everywhere else) - what do the olefins do?
Olefins = Alkenes? An alkene is any hydrocarbon with one or more C=C (double) bonds. (an unsaturated hydrocarbon)
eg, H2C=CH2 (Ethene) and H2C=CH-CH3 (Propene)
AlkEnes do not burn as cleanly as AlkAnes due to the lower C:H ratio, and can produce more soot (Solid carbon deposits)
Alkenes can also undergo polymerisation reactions to form 'Gum' (insoluble deposits in the fuel system)
Alkenes are somewhat favourable for fuel companies to add to fuel because they can increase the octane rating of a fuel (reduce knocking potential).
I had to look up olefin too. It's an alkene, apparently.
As you say an alkene will need more oxygen and may produce soot. It's also more energy dense per g.
I'm not aware of any alkynes worth talking about other than acetylene and that's far too valuable to throw away in petrol.
Anecdotal tip - you know the old "lawnmower won't start, squirt some WD40 in the spark plug hole" trick? This works because WD40 is a mixture of light oil in abuot 70% naptha. Naptha is the very volatile bit of petrol, so C4-C5-C6, it is a bit prone to evaporation so not much use in liquid fuel. However it is EXTREMELY flammable, hence why a quick squirt of it will get a badly set up or gummed up lawnmower going after a winter in the shed and the carb half clogged with old fuel.
As you say an alkene will need more oxygen and may produce soot. It's also more energy dense per g.
I'm not aware of any alkynes worth talking about other than acetylene and that's far too valuable to throw away in petrol.
Anecdotal tip - you know the old "lawnmower won't start, squirt some WD40 in the spark plug hole" trick? This works because WD40 is a mixture of light oil in abuot 70% naptha. Naptha is the very volatile bit of petrol, so C4-C5-C6, it is a bit prone to evaporation so not much use in liquid fuel. However it is EXTREMELY flammable, hence why a quick squirt of it will get a badly set up or gummed up lawnmower going after a winter in the shed and the carb half clogged with old fuel.
rainmakerraw said:
Unlike in the USA - where fuel companies fall over themselves to provide lots of technical data and information about the base stock and additives etc - the UK seems to be under a blanket of corporate silence and absolutely everything is a 'trade secret' leaving drivers to just pay their money and make their choice.
AFAIK there are only a handful of refineries that supply the garages, so suspect that the end 95 RON product is pretty similar whether you go to BP, Shell, Sainsburys or Asda.mcflurry said:
rainmakerraw said:
Unlike in the USA - where fuel companies fall over themselves to provide lots of technical data and information about the base stock and additives etc - the UK seems to be under a blanket of corporate silence and absolutely everything is a 'trade secret' leaving drivers to just pay their money and make their choice.
AFAIK there are only a handful of refineries that supply the garages, so suspect that the end 95 RON product is pretty similar whether you go to BP, Shell, Sainsburys or Asda.Isn't there a minimum fuel "standard" for each variant prescribed by the British Standards Institute?
That is probably to ensure a degree of compatibility rather than to provide specific energy densities.
I work in upstream oil & gas (the getting it out of the ground bit) so know bugger all about refinery process. We give up at anything more complex than 3-phase separation or basic sours stripping. Interested to learn more about the other end of the process though.
I could probably talk you through most of the stuff from dying dinosaur to the refinery gates though if needed.
I could probably talk you through most of the stuff from dying dinosaur to the refinery gates though if needed.
Evilex said:
Quite. There are only a few refineries.
Isn't there a minimum fuel "standard" for each variant prescribed by the British Standards Institute?
That is probably to ensure a degree of compatibility rather than to provide specific energy densities.
Put it this way Shell haven't operated a refinery in the uk for probably 6-7 years since they offloaded Stanlow where I use to work and was directly involved in the loading terminal. Base fuel is absolutely identical Isn't there a minimum fuel "standard" for each variant prescribed by the British Standards Institute?
That is probably to ensure a degree of compatibility rather than to provide specific energy densities.
A few things to note, all petrol sold in the UK conforms to the European standard EN228.
Nobody sells fuel that does not conform to this standard, that would be illegal and they would be jailed.
There is no real qualitative difference between gasoline sold by known oil company brands and that sold at supermarkets. Most often the oil will come from the same importer who buys on the international markets. The UK refining industry has been run down quite considerably, most people think BP and Shell refine oil in the UK and then sell it at their branded outlets. They don't, they import a little from thier European plants but mostly they buy from the same importer as the supermarkets.
Some brands , be they supermarkets or oil companies, will put in their own additives in "at the rack" (ie when the petrol is loaded at the import terminal/refinery onto a road tanker)with various claims about cleaning your engine and so forth. While these are unlikely to harm your engine I don't believe they really do much good, they are just a way of trying to differentiate a product which by law is generic in most qualities.
So really the only place to distinguish between brands is on their "posh" petrol. This has higher octane expressed as RON as well as more additives about which they make the usual claims. These conform to standard BS7800 which mandates 97 RON (like BP Ultimate) . Some manufacturers go higher though Shell V Power is i think 98 octane and Tesco even do a 99. These fuels are best for classic cars, fast n/a piston engines, sports bikes etc. I put Tesco 99 in mine as first choice, or V Power then Ultimate. Most cars though are made to run on 95 octane EN225 so i doubt most of us would feel any benefit of the high octane stuff. My modern non exotics only ever get "vin ordinaire".
The other thing that concerns people is bio Ethanol, all UK petrol has a maximum of 5% and ALL sellers will maximize that, its cheaper than gasoline and not to do so would be giving money away.In Europe they have introduced E10 which has 10% Ethanol. Anecdotal evidence suggests that fuel consumption is effected and that you maybe better off filling up with "posh" on your way to Le mans. As I understand it there are no plans for the UK to go down the 10% route. Some say that even 5% Ethanol makes for a poorer petrol that we used to get, often blaming it when a tuned engine gives up in a spectacular way. I suspect that is what the guy who sold them the tuning bits tells them.
Nobody sells fuel that does not conform to this standard, that would be illegal and they would be jailed.
There is no real qualitative difference between gasoline sold by known oil company brands and that sold at supermarkets. Most often the oil will come from the same importer who buys on the international markets. The UK refining industry has been run down quite considerably, most people think BP and Shell refine oil in the UK and then sell it at their branded outlets. They don't, they import a little from thier European plants but mostly they buy from the same importer as the supermarkets.
Some brands , be they supermarkets or oil companies, will put in their own additives in "at the rack" (ie when the petrol is loaded at the import terminal/refinery onto a road tanker)with various claims about cleaning your engine and so forth. While these are unlikely to harm your engine I don't believe they really do much good, they are just a way of trying to differentiate a product which by law is generic in most qualities.
So really the only place to distinguish between brands is on their "posh" petrol. This has higher octane expressed as RON as well as more additives about which they make the usual claims. These conform to standard BS7800 which mandates 97 RON (like BP Ultimate) . Some manufacturers go higher though Shell V Power is i think 98 octane and Tesco even do a 99. These fuels are best for classic cars, fast n/a piston engines, sports bikes etc. I put Tesco 99 in mine as first choice, or V Power then Ultimate. Most cars though are made to run on 95 octane EN225 so i doubt most of us would feel any benefit of the high octane stuff. My modern non exotics only ever get "vin ordinaire".
The other thing that concerns people is bio Ethanol, all UK petrol has a maximum of 5% and ALL sellers will maximize that, its cheaper than gasoline and not to do so would be giving money away.In Europe they have introduced E10 which has 10% Ethanol. Anecdotal evidence suggests that fuel consumption is effected and that you maybe better off filling up with "posh" on your way to Le mans. As I understand it there are no plans for the UK to go down the 10% route. Some say that even 5% Ethanol makes for a poorer petrol that we used to get, often blaming it when a tuned engine gives up in a spectacular way. I suspect that is what the guy who sold them the tuning bits tells them.
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