Help me learn more about petrol
Discussion
I'm definitely no expert on this, but I have heard from many sources that the base fuels are the same.
What I did want to say, is that I am convinced that some of the additives do work.
I can remember my dad telling me about having to decoke engines many years ago, and the carbon deposits in engines decreased performance considerably over time.
In the last 30 years, engines manage to perform perfectly well over hundreds of thousands of miles without ever being stripped down, so I do think the detergent additives have helped our engines.
I also seem to remember a post on Pistonheads about carbon build up in the inlet ports of a direct injection engine, because the fuel wasn't cleaning away the oil from the crankcase breather.
I do tend to buy branded fuels for the additives, 95 for our regular cars and 97 for my Caterham as it gets used a lot harder.
What I did want to say, is that I am convinced that some of the additives do work.
I can remember my dad telling me about having to decoke engines many years ago, and the carbon deposits in engines decreased performance considerably over time.
In the last 30 years, engines manage to perform perfectly well over hundreds of thousands of miles without ever being stripped down, so I do think the detergent additives have helped our engines.
I also seem to remember a post on Pistonheads about carbon build up in the inlet ports of a direct injection engine, because the fuel wasn't cleaning away the oil from the crankcase breather.
I do tend to buy branded fuels for the additives, 95 for our regular cars and 97 for my Caterham as it gets used a lot harder.
What I find interesting is that the US military has essentially moved to a single fuel for ALL of its vehicles. It's called JP-8 and gives them a huge logistical advantage in not needing multiple "flavours" of fuel in their supply chain. As you might have guessed, JP stands for Jet Propellant. It's a modified jet fuel which burns fine in gas turbines (aircraft, ships, tanks) and also works in diesel engined vehicles.
The Russian military takes a somewhat different approach with "multi-fuel" engines. In other words they set their vehicles up to be able to burn any old crap that's available from time to time.
Same problem - different solutions.
The Russian military takes a somewhat different approach with "multi-fuel" engines. In other words they set their vehicles up to be able to burn any old crap that's available from time to time.
Same problem - different solutions.
luckystrike said:
A quick question about diesel for the chemists - I understand that diesel is engineered to have a low octane rating for the specific purpose of detonating easily, and that the equivalent performance rating to a petrol's RON value is the cetane rating. What does this actually mean? As in, if a high octane petrol is more resistant to detonation, what makes a higher cetane rating diesel better than its lower rated equivalent?
AIUI, RON comes from a standard knock suppression test on a hexane-octane mix. As diesel is in the region of decane-cetane, that test doesn't apply.Cetane rating is similar, using Cetane (duh, C16-H34) and heptamethylnonane (C16-H34, but a very different structure). It looks like a higher rate gives more thorough combustion and less of that Rolling Coal nonsense.
CN=percent n-cetane + 0.15*percent HMN.
If I'm talking out of my bung, there'll be an expert along in a minute.
I do know that refineries will blend different crude oils and gases to boost the octane rather than add olefins due to the cost of olefins. And in winter the butane content increases as it is more dense in cold weather. Butane is cheaper than olefins and boosts the octane rating. So when there's a real cold spell and the demand for gas for heating increases the price of fuel will also go up - as the butane price is higher.
And yes, refineries make petrol for anyone who is prepared to buy it.
Probably not much use but that's all I can remember from refining 25 yrs ago. That and that duty is paid at the gate so the tanks would be empty at the refinery for budget day so that any increase in duty went straight to the oil companies coffers and not the Chancellor's!
And yes, refineries make petrol for anyone who is prepared to buy it.
Probably not much use but that's all I can remember from refining 25 yrs ago. That and that duty is paid at the gate so the tanks would be empty at the refinery for budget day so that any increase in duty went straight to the oil companies coffers and not the Chancellor's!
BrassMan said:
AIUI, RON comes from a standard knock suppression test on a hexane-octane mix. As diesel is in the region of decane-cetane, that test doesn't apply.
Cetane rating is similar, using Cetane (duh, C16-H34) and heptamethylnonane (C16-H34, but a very different structure). It looks like a higher rate gives more thorough combustion and less of that Rolling Coal nonsense.
CN=percent n-cetane + 0.15*percent HMN.
If I'm talking out of my bung, there'll be an expert along in a minute.
Cracking, it at least sounds sensible if that helps! Thank you.Cetane rating is similar, using Cetane (duh, C16-H34) and heptamethylnonane (C16-H34, but a very different structure). It looks like a higher rate gives more thorough combustion and less of that Rolling Coal nonsense.
CN=percent n-cetane + 0.15*percent HMN.
If I'm talking out of my bung, there'll be an expert along in a minute.
I spent the last few years working in a Highways dept in Plymouth. One of the things I noticed was the large variety of different brands of fuel tankers that came out of the Greenergy depot on Cattedown Road.
There are a few storage units there, but they're not branded, so I'm pretty convinced they were all the same base fuel and so any difference was in the additives.
I've also put various fuels in the maser and the Z4M (which is supposed to prefer 98 RON) and use normal 95 RON supermarket fuel as I've not noticed any difference, except perhaps I got and extra 1-1.5mpg in France and Spain running the maser on 98 RON as I gather it doesn't contain (as much) ethanol and is better for the rubber bits.
Having said that, 1mpg is a 5% improvement.
There are a few storage units there, but they're not branded, so I'm pretty convinced they were all the same base fuel and so any difference was in the additives.
I've also put various fuels in the maser and the Z4M (which is supposed to prefer 98 RON) and use normal 95 RON supermarket fuel as I've not noticed any difference, except perhaps I got and extra 1-1.5mpg in France and Spain running the maser on 98 RON as I gather it doesn't contain (as much) ethanol and is better for the rubber bits.
Having said that, 1mpg is a 5% improvement.
HJE said:
I do know that refineries will blend different crude oils and gases to boost the octane rather than add olefins due to the cost of olefins. And in winter the butane content increases as it is more dense in cold weather. Butane is cheaper than olefins and boosts the octane rating. So when there's a real cold spell and the demand for gas for heating increases the price of fuel will also go up - as the butane price is higher.
Yes, in addition to the change in fuel for different seasons (I'm sure someone can elaborate on the basic difference in blends for summer, winter and in between), the makeup of the fuel will change according to market conditions, plant status, feedstock and other factors. Sometimes however if the plant is running poorly (industrial fractionating columns and crackers are not exactly precision instruments and can have all sorts of things affecting their performance and outputs), demand conditions for other or if there is a feedstock problem, then the amount of olefins used may be significantly higher, regardless of their cost.Additives can be highly specialised and although some are added post-refining, some may be used for production reasons and be part of every litre that originates from the plant, regardless of final branding.
An example would be a process chemical aimed at boosting the overall marketability of the grades produced by the plant i.e. Instead of 30% heavy grades (waxes/lubricants etc.), 40% fuel oil and 30% petrol/diesel (not realistic example) the use of additives and/or catalysts somewhere in the process may boost 5% of the fuel oil to meet the broad characteristics of the much more profitable diesel or petrol grades, more than paying for the expensive additive used.
However, sometimes this can come at the cost of a shorter useful lifespan for the 'boosted' fuel, meaning it may 'go off' more quickly (although still within statutory limits) than less highly processed fuel.
Interestingly, the bulk purchasers (the retailers) will have limited or zero visibility of such process changes. All the refiner is guaranteeing is that the fuel meets the specs set out by the customer. The methods used to achieve that can and do vary, and indeed may be commercially sensitive.
This all means that "Shell V-Power" (or whatever) is in effect lots of different fuels, depending on when and where you buy it. All that is done is to manipulate the characteristics of the final product to match a set of pre-defined criteria for that fuel by use of the various additives or processing decisions. This starts with EN 228, but may include higher target RON and/or MON, volatility, oxygen content, ethanol mix and others too.
loudlashadjuster said:
This all means that "Shell V-Power" (or whatever) is in effect lots of different fuels, depending on when and where you buy it. All that is done is to manipulate the characteristics of the final product to match a set of pre-defined criteria for that fuel by use of the various additives or processing decisions. This starts with EN 228, but may include higher target RON and/or MON, volatility, oxygen content, ethanol mix and others too.
Careful with those claims.VPower comes from a single source, regardless of where it's being retailed.
If you have any particular papers you would like to read but can't access I have access to pretty much everything through university (unfortunately I don't do Chem, although I do have a few ChemEng friends). I am going to see if I can find anything good and if so will download and email them to you if you would like.
ETA: Perhaps not surprising but there is a large quantity of research produced since 2000 on fuel compositions and aromatic levels relating to combustion properties in diesel engines but there is not so much out there on petrol. I suspect this is because a lot of the research was done in the 60's - 80's/90's so I shall look further back.
ETA: Perhaps not surprising but there is a large quantity of research produced since 2000 on fuel compositions and aromatic levels relating to combustion properties in diesel engines but there is not so much out there on petrol. I suspect this is because a lot of the research was done in the 60's - 80's/90's so I shall look further back.
Edited by patch5674 on Thursday 7th July 00:45
Ozzie Osmond said:
The Russian military takes a somewhat different approach with "multi-fuel" engines. In other words they set their vehicles up to be able to burn any old crap that's available from time to time.
Same problem - different solutions.
Most military vehicles are multi-fuel at the larger end. Certainly British tanks and the like are multi-fuel. The ability to grab whatever sSame problem - different solutions.
t is close by is a much bigger advantage than having a single fuel type for all machines and having to truck it in. I suspect, but havent checked, US battle tanks and forward military vehicles are almost certainly multi-fuel also. As far as refining goes there are only 6 in the UK, and almost all fuels are bought from whichever is most convenient. All the companies have trading departments and will buy and sell in the wholesale and retail totally separately, meaning that BP fuel on the forecourt could be from Total's refinery. A base stock will be refined, and then additives added when the fuel is mixed into the lorry, depending on the customer and spec required. A lot of fuel is obviously imported, and part of the reason that diesel has come down close to the cost of petrol is new refineries in the Middle East which can produce low sulphur diesel to EU spec, when previously the product they produced wasnt high enough quality to import.
UK refineries
United Kingdom
England
Coryton Refinery (Petroplus), 175,000 bbl/d (27,800 m3/d) shutdown;converted to terminal in 2012
Fawley Refinery (ExxonMobil), 330,000 bbl/d (52,000 m3/d)
Humber Refinery (Phillips 66), 221,000 bbl/d (35,100 m3/d)
Lindsey Oil Refinery (Total), 223,000 bbl/d (35,500 m3/d)
Teesside Refinery (Petroplus), 117,000 bbl/d (18,600 m3/d) Closed 2009
Stanlow Refinery (Essar Oil), 272,000 bbl/d (43,200 m3/d)
Scotland
Grangemouth Refinery (Petroineos, a joint venture of Ineos and PetroChina), 205,000 bbl/d (32,600 m3/d)
Wales
Milford Haven Refinery (Murco),135,000 bbl/d (21,500 m3/d) Closed in November 2014
Pembroke Refinery (Valero), 215,000 bbl/d (34,200 m3/d)
If you are serious I have downloaded the 2 chapters relating to fuel from the following textbook-
The internal-combustion engine in theory and practice. Volume 2, Combustion, fuels, materials, design.
Charles Fayette Taylor., Cambridge, Mass. : M.I.T. Press 2nd ed., rev. 1985
I have not had a chance to look at them properly myself yet as each chapter is about 50 pages of A4 long. Although probably only about 30% relevant as it talks about composition of natural gas fuels as well as solid fuel and touches upon aviation fuel.
If you PM me your email I am happy to send over have as PDF.
The internal-combustion engine in theory and practice. Volume 2, Combustion, fuels, materials, design.
Charles Fayette Taylor., Cambridge, Mass. : M.I.T. Press 2nd ed., rev. 1985
I have not had a chance to look at them properly myself yet as each chapter is about 50 pages of A4 long. Although probably only about 30% relevant as it talks about composition of natural gas fuels as well as solid fuel and touches upon aviation fuel.
If you PM me your email I am happy to send over have as PDF.
Some related comments on Ethanol from my experience working on classic cars. Ethanol is also a solvent and is commonly used in many cleaners for example carb cleaner. It therefore does a great job of removing all of the gunk on the bottom of your fuel tank and ultimately shoving it through your fuel pump, fuel filters and carbs, especially if you leave it over the winter. It can block needle valves and cause your carbs to overflow. It has a shelf life of c. three months. It's also hygroscopic and can seperate over time leaving a corrosive layer of ethanol/water at the bottom of the tank. You want to hear a car trying to run on that crap!
Ethanol also lowers the boiling point of fuel which on a carburetted car can lead to early boiling of the fuel/vapour lock depending on how ancient your car is and how unprepared it is for modern fuels and modern traffic. Ethanol also eats certain types of seals over time. I'm currently designing a modified fuel system for one of my cars to get over the issues caused with variable fuel and the impact of ethanol. On most cars mid 1960's and onwards the effect is less marked than say cars up to the 50's which normally have poor heat protection and poor cooling/engine design/engine bay layout which contributes to vapour lock.
One of the other things adding Ethanol does which is less known is it increases the burn time which in turn requires an engine to run more initial advance at idle to ensure proper combustion. This then normally requires the distributor to be recurved if the engine is to have a chance at running properly throughout the rev range. Ethanol has only about 57% of the energy in BTU of petrol. Higher compression engines deal better with higher Ethanol mixes and why I suspect we are starting to see some NA engines coming out with very high compression ratios compared to those of say the last decade. It's a move to support cleaner burning fuels at the expense of fuel economy.
Most of these issues I've mentioned do not affect modern cars, but have a big impact on classics. Modern cars run pressurised fuel systems which raise the boiling point and have the capability to monitor and adjust timing and don't run the type of seals that are as easily effected by ethanol. A bit of advice for classic owners would be to run your tank as low as possible before storing away for the winter, or better empty it completely. Better yet if you can buy Ethanol free fuel in your area, seek it out.
Anyway, just my experience and sorry no chemistry!
Ethanol also lowers the boiling point of fuel which on a carburetted car can lead to early boiling of the fuel/vapour lock depending on how ancient your car is and how unprepared it is for modern fuels and modern traffic. Ethanol also eats certain types of seals over time. I'm currently designing a modified fuel system for one of my cars to get over the issues caused with variable fuel and the impact of ethanol. On most cars mid 1960's and onwards the effect is less marked than say cars up to the 50's which normally have poor heat protection and poor cooling/engine design/engine bay layout which contributes to vapour lock.
One of the other things adding Ethanol does which is less known is it increases the burn time which in turn requires an engine to run more initial advance at idle to ensure proper combustion. This then normally requires the distributor to be recurved if the engine is to have a chance at running properly throughout the rev range. Ethanol has only about 57% of the energy in BTU of petrol. Higher compression engines deal better with higher Ethanol mixes and why I suspect we are starting to see some NA engines coming out with very high compression ratios compared to those of say the last decade. It's a move to support cleaner burning fuels at the expense of fuel economy.
Most of these issues I've mentioned do not affect modern cars, but have a big impact on classics. Modern cars run pressurised fuel systems which raise the boiling point and have the capability to monitor and adjust timing and don't run the type of seals that are as easily effected by ethanol. A bit of advice for classic owners would be to run your tank as low as possible before storing away for the winter, or better empty it completely. Better yet if you can buy Ethanol free fuel in your area, seek it out.
Anyway, just my experience and sorry no chemistry!
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.
Edited by loudlashadjuster on Thursday 7th July 07:02
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.
Very interesting thread so thanks OP and all the other contributors.
Possibly not directly related but close, can anyone comment on why with the advent of direct fuel injection, manufacturers have re-introduced carbon build up or what used to be known as coking? I'd assumed this had been banished to the annals of motoring history long ago but seems to be a very much real problem again.
Can the fuel manufacturers do anything to fix this problem? I've heard certain fuels with cleaning additives might be better at preventing this?
Possibly not directly related but close, can anyone comment on why with the advent of direct fuel injection, manufacturers have re-introduced carbon build up or what used to be known as coking? I'd assumed this had been banished to the annals of motoring history long ago but seems to be a very much real problem again.
Can the fuel manufacturers do anything to fix this problem? I've heard certain fuels with cleaning additives might be better at preventing this?
Guvernator said:
Very interesting thread so thanks OP and all the other contributors.
Possibly not directly related but close, can anyone comment on why with the advent of direct fuel injection, manufacturers have re-introduced carbon build up or what used to be known as coking? I'd assumed this had been banished to the annals of motoring history long ago but seems to be a very much real problem again.
Can the fuel manufacturers do anything to fix this problem? I've heard certain fuels with cleaning additives might be better at preventing this?
I was talking with a couple of fuels technologists a couple of weeks ago - whilst 'coking' was largely eliminated, the spray jets on a modern direct injection engine are very fine and a very specific pattern to ensure the cleanest burn possible. It does't take a lot of carbon build up / other combustion deposits to adversely affect the spray pattern by fully or partially blocking jets. This is why a significant amount of money is invested in cleaning additives.Possibly not directly related but close, can anyone comment on why with the advent of direct fuel injection, manufacturers have re-introduced carbon build up or what used to be known as coking? I'd assumed this had been banished to the annals of motoring history long ago but seems to be a very much real problem again.
Can the fuel manufacturers do anything to fix this problem? I've heard certain fuels with cleaning additives might be better at preventing this?
Guvernator said:
Very interesting thread so thanks OP and all the other contributors.
Possibly not directly related but close, can anyone comment on why with the advent of direct fuel injection, manufacturers have re-introduced carbon build up or what used to be known as coking? I'd assumed this had been banished to the annals of motoring history long ago but seems to be a very much real problem again.
Can the fuel manufacturers do anything to fix this problem? I've heard certain fuels with cleaning additives might be better at preventing this?
It is a phenomenon of DI (both wall and spray guided).Possibly not directly related but close, can anyone comment on why with the advent of direct fuel injection, manufacturers have re-introduced carbon build up or what used to be known as coking? I'd assumed this had been banished to the annals of motoring history long ago but seems to be a very much real problem again.
Can the fuel manufacturers do anything to fix this problem? I've heard certain fuels with cleaning additives might be better at preventing this?
With PFI the fuel and air are premixed upstream of the valve and arrive in the combustion chamber as a mixture. All fine and dandy for burning as you have a nice mixture.
With DI, the fuel is sprayed directly in to the combustion chamber, effectively as a gas, but when it comes in to contact with the bore or the piston it re-forms as a liquid. This liquid then does not burn properly and turns to carbon due to the incomplete combustion. Over time this builds up. It is also the reason that for later EU6 (c/d?) regulations petrol cars with DI are more than likely going to need a GPF (gasoline particulate filter) as they emit particulates in a similar way to a diesel. This is why some DI engines have PFI as well - to reduce emissions during part load operation.
stavers said:
It is a phenomenon of DI (both wall and spray guided).
With PFI the fuel and air are premixed upstream of the valve and arrive in the combustion chamber as a mixture. All fine and dandy for burning as you have a nice mixture.
With DI, the fuel is sprayed directly in to the combustion chamber, effectively as a gas, but when it comes in to contact with the bore or the piston it re-forms as a liquid. This liquid then does not burn properly and turns to carbon due to the incomplete combustion. Over time this builds up. It is also the reason that for later EU6 (c/d?) regulations petrol cars with DI are more than likely going to need a GPF (gasoline particulate filter) as they emit particulates in a similar way to a diesel. This is why some DI engines have PFI as well - to reduce emissions during part load operation.
So in effect they introduced DI to improve efficiency\fuel economy but in doing so have made emissions\pollution worse. I've often heard that fuel efficiency and low emissions are mutually exclusive which seems a bit counter-intuitive. You'd also think after a 100 years of constant R&D they'd have cracked a lot of these issues although I guess the quest for better efficiency and lower emissions has only come to the fore in the last 15 years.With PFI the fuel and air are premixed upstream of the valve and arrive in the combustion chamber as a mixture. All fine and dandy for burning as you have a nice mixture.
With DI, the fuel is sprayed directly in to the combustion chamber, effectively as a gas, but when it comes in to contact with the bore or the piston it re-forms as a liquid. This liquid then does not burn properly and turns to carbon due to the incomplete combustion. Over time this builds up. It is also the reason that for later EU6 (c/d?) regulations petrol cars with DI are more than likely going to need a GPF (gasoline particulate filter) as they emit particulates in a similar way to a diesel. This is why some DI engines have PFI as well - to reduce emissions during part load operation.
Do any of the cleaning additives in fuel actually do anything to combat the carbon buildup issue though? Again I've heard conflicting reports.
Spannerski said:
Very interesting thread and I applaud your scientific approach. Unlike mine for adding acetone to fuel to get a boost in economy.
I took the approach that there are so many threads on forums across the internet extolling the benefits of adding acetone (and just as many not)
I decided to give it a go.
3 vehicles. One a 1.6 ti-VCT Ford Focus (variable cam timing, stnd FI) a high mileage Rover 400 1.4 (Stnd FI, cat etc... 175K on the clock) and a Honda VF500 Motorcycle of 1987 vintage (V4 motor, 4 carbs, 4 cams, 16v and 11,500 rpm). so a broad range of vehicles to test.
I tried different quantities per tank and different ways of adding it over a couple of years comparing tanks with it added and tanks without and came to the following conclusions:
Ford Focus, improvement in mpg = 0%
Rover 400, improvement in mpg = 0%
Honda VF 500, improvement in mpg = 0%
If anyone else has tried this with better/worse results, please let me know what you did, ratio mix etc... as I have a large container of acetone left and don't wear nail polish.
I would also like to point out that I have no affiliation with any major/minor fuel company or automotive manufacturer as often cited by advocates of Acetone in fuel flame wars to those who say it doesn't work.
Cheers
Not really a broad range of vehicles. All relatively low tune, naturally aspirated petrol engines.I took the approach that there are so many threads on forums across the internet extolling the benefits of adding acetone (and just as many not)
I decided to give it a go.
3 vehicles. One a 1.6 ti-VCT Ford Focus (variable cam timing, stnd FI) a high mileage Rover 400 1.4 (Stnd FI, cat etc... 175K on the clock) and a Honda VF500 Motorcycle of 1987 vintage (V4 motor, 4 carbs, 4 cams, 16v and 11,500 rpm). so a broad range of vehicles to test.
I tried different quantities per tank and different ways of adding it over a couple of years comparing tanks with it added and tanks without and came to the following conclusions:
Ford Focus, improvement in mpg = 0%
Rover 400, improvement in mpg = 0%
Honda VF 500, improvement in mpg = 0%
If anyone else has tried this with better/worse results, please let me know what you did, ratio mix etc... as I have a large container of acetone left and don't wear nail polish.
I would also like to point out that I have no affiliation with any major/minor fuel company or automotive manufacturer as often cited by advocates of Acetone in fuel flame wars to those who say it doesn't work.
Cheers
On a modern direct injection turbo petrol you will notice a difference.
The amount of extra timing you can run with a 99 octane can account for 30 or 40bhp when you have tuned the car.
EG, mk5 Golf Ed 30. Stock 235bhp ish.
Remap on 95 octane - 270 maybe?
Remap on 99 octane - 295-305 all day.
I noticed much more responsive driving experience and increased MPG even on my standard Mk5 GTI.
It also seems to help keep carbon build up at bay.
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