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
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.
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?
Some absolutely fantastic replies here folks! Far too many (and too much) to quote individually, but rest assured they've all been read and taken on board. I've already learnt a lot, and have a lot more I can read up on now. Thank you. Feel free to keep it coming! PH ranks very highly on Google, so it'd be nice to have a decent informed thread on page 1 rather than the guff that's there presently.
Feel free to keep it coming! PH ranks very highly on Google, so it'd be nice to have a decent informed thread on page 1 rather than the guff that's there presently. Trabi601 said:
loudlashadjuster said:
Trabi601 said:
Careful with those claims.
VPower comes from a single source, regardless of where it's being retailed.
Nothing I said contradicts that.VPower comes from a single source, regardless of where it's being retailed.
Also, while it is also my understanding is that Stanlow produces all V-Power, this obviously only applies to the UK.
There's some good stuff coming out in this thread, I'm enjoying the read. Patch5674 I've emailed you, thanks!
KuroKeeper said:
Great thread, OP! Sorry for being late to the discussions. I'm a fuels technologist with a chemistry and engineering background so am more than happy to answer any and all your questions!
I'd say these are the key things to know about petrol in the UK (many of which have already been stated):
- All petrol in the UK meets BS EN 228 (and diesel BS EN 590). These specifications guarantee a minimum QUALITY level, but have no PERFORMANCE requirements. It is important to understand this distinction. The right quality fuel can still result in engine deposits as this is not a mandated requirement.
- As said by others, all petrol comes from a system that meets the above spec but can still have variations in fuel composition (olefins, aromatics, etc.)
- To answer one of the OPs original questions: increased density does not necessarily result in increased calorific value - it depends on the composition.
- Octane grade stated at the pump is RON and specifies a minimum. Increased octane can be of benefit if your vehicle is calibrated to respond to >95 RON (like my GT86 is!)
- Fuel additives can result in benefits (such as cleaning injectors and intake valves) but it's not the case that having "some" additive in there is the answer. Fuels formulation is a balancing act so check which tests were run by a given supplier/brand to prove they work.
Please ask if you want to know more!
Thanks! Sorry for the delay replying but my hands have been pretty full. You just might regret that haha. Fuels technologist sounds like something very interesting indeed; I imagine you develop fuels and/or additives for one of the majors. I'd be very happy to be able to download your knowledge into my brain but alas, since the opportunity has arisen I'll have to make do with asking a few questions. I hope I don't bore you! I'd say these are the key things to know about petrol in the UK (many of which have already been stated):
- All petrol in the UK meets BS EN 228 (and diesel BS EN 590). These specifications guarantee a minimum QUALITY level, but have no PERFORMANCE requirements. It is important to understand this distinction. The right quality fuel can still result in engine deposits as this is not a mandated requirement.
- As said by others, all petrol comes from a system that meets the above spec but can still have variations in fuel composition (olefins, aromatics, etc.)
- To answer one of the OPs original questions: increased density does not necessarily result in increased calorific value - it depends on the composition.
- Octane grade stated at the pump is RON and specifies a minimum. Increased octane can be of benefit if your vehicle is calibrated to respond to >95 RON (like my GT86 is!)
- Fuel additives can result in benefits (such as cleaning injectors and intake valves) but it's not the case that having "some" additive in there is the answer. Fuels formulation is a balancing act so check which tests were run by a given supplier/brand to prove they work.
Please ask if you want to know more!
- Despite internet urban legend, I'm fairly confident all fuel supplied in the UK meets at least a modicum of performance regarding additives. In my case it's not really a concern as I run a brand new (i.e. 'clean') car on 99 RON fuels - both of which state they have multitudes more additives than their own respective base 95 RON fuel. I do note, however, that you made reference to it being a case of finely balancing the 'ingredients' rather than just throwing in 'some additive'. Does this mean adding things like Miller's Petrol EcoMax (or RedEx, or whatever) is fairly frivolous and not worth bothering with? For example, Millers assured me in writing that their additive would 'definitely' increase any UK fuel by 2 RON, giving effectively 101 RON fuel added to either Shell or Greenergy/Tesco 99. It would also guarantee standardised lubricity and detergency, they add, and could therefore be a cost effective alternative to buying V-Power. If I opted instead for Costco 97 RON (which is 107.9ppl versus 117.9ppl in these parts) and added Petrol EcoMax, they assured me it'd bring it to 99 RON with a full detergent pack. I tried it for a tank and didn't find it very effective however, with a loss of low down torque and high end power compared to the genuine 'full fat' stuff. Hence the question sparked by your comment.
- Giving further consideration to the two fuels in my OP (Momentum 99 and V-Power), just because they're both 99 RON and meet the requirements of my car. I have no doubt that Royal Dutch Shell and Greenergy put in a great deal of effort to making their respective fuels as good as they can, whether to a price point or to an intended performance standard. Shell does publicise the ISO tests it subjects its fuels to in order to ensure they're good at combating 'gunk and corrosion' (as they term it). Greenergy - via Tesco - have assured me they carry out similar industry standard testing on their own fuels, but that they feel the majority of customers are more concerned with EMPEEGEES than performance, so that's where they focus their literature and claims. That aside, for a modern turbo engine (2.0 TSI 220ps in my case) would it be better in power and economy terms to run on the higher MON, higher oxygenates, lower olefin/alkene fuel (M99) or on the slightly lower MON, less dense, lower oxygenate but higher olefin/alkene fuel (VPower)? Or is it a case of rolling the dice as it's impossible to say? As per my earlier comments, I don't actually find much between them in the real world, and since M99 is a fiver a tank cheaper I tend to stick to that lately. However, I can't shake the thought that Shell have a hell of a lot more experience and quite possibly a higher quality, more consistent end product. Could you add any comments, information or ideas? I realise your professional (and/or academic) affiliations may tie your hands somewhat here.
At the end of the day the price of petrol is still fairly trivial, certainly for me with my mileage and attitude to driving. I'd rather spend an extra £10 or £20 a week on 'expensive' branded petrol for hooning in the car than going to the pub/football/smoking/drinking/whatever. As with most drivers, I just want what's best for my car and to buy the fuel that will give me the most consistent power, torque, cleanliness - and yes, even economy benefits. I also just happen to have an insane thirst for learning new stuff, so feel free to give me both barrels about fuels/additives/whatever if you're in the mood for typing. I'm not lazy and would be just as happy to buy some textbooks or read some websites if you have any pointers that would save you time.
Cheers!
mikeN54 said:
I'm not saying they all do that, but many do and the claims are all a bit wishy washy.
I was aware of that, which is why I emailed them to ask in the first place. I asked if they meant 2 RON (i.e. 97 to 99) and they replied that it 'definitely increases fuel by 2 octane', but like you I really don't see how adding something 1:1000 would do so! On reflection I notice they specifically said '2 octane' and not '2 RON' or '2 points'. Weasel words, perhaps?Gassing Station | General Gassing | Top of Page | What's New | My Stuff