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I thought this had been done to death so many times before.
The definitive answer then (unless something's changed) was the fuel's the same apart from the additives put in at the point of delivery.
HJ used to advocate the use of Shell and Texaco.
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Tom-
Any info as to the nature and quantity of these additives...? EN590 diesel isn't exactly raw crude as it is.
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Sorry, can't help you.
I recall someone on here, claiming to be a fuel tanker driver, said the same fuel's delivered to all retail outlets. It's just what's added to the different branded fuel stations at the time of delivery.
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I'd be really surprised if anything was added to the fuel by the staff at the forecourt. Without wanting to cast aspersions, the liability concerns are just too big to entrust the integrity of a tank of fuel to the checkout staff. And I can't see the tanker driver pratting around with a measuring jug, pipette and a bottle of SECRET ADDITIVE-FOR PREMIUM PUMPS ONLY!!! NO GIRLS ALLOWED!!
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If anyone thinks I have a vendetta against 'premium' fuels then they're right. Numerous consumer organisations have been telling people for years to stop wasting their money on supposedly high performance fuels. Numerous independant tests have shown no statistically significant difference in fuel economy. Yet the venders still peddle the stuff based on unfounded insinuation and rumour. Tesco momentum is the most egregious example-claiming up to 25% more miles per gallon compared to Tesco regular. The only honest part of the statement is the 'up to' which means less than. Anyone who understands engines will tell you that you don't make substantial increases in efficiency by changing the fuel. To make 25% more mpg would require changing the calorific value of the fuel by about 25% which is impossible.
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Unthrottled, your imagined picture is a little over the top, but, in essence (!) it's correct.
I had a discussion with a BP tanker driver a while back. Apparently, when the tanker pulls in to the fuel depot (in this case, it was the notorious Buncefield in Hemel Hempstead), the driver adds BP's potion to it before filling up and driving off to deliver to the various forecourts.
Edited by ChrisPeugeot on 16/05/2011 at 16:40
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Gosh! But that means that the base fuel is the same-and hence the calorific value of the fuel is the same-so no reason for more mpg.
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I share your scepticism, but admit to using Miller's with my diesel, I suppose for added piece of mind; it's not a logical thing.
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Modern road tankers are not one big tank but are a number of tanks;this caused problems several years ago when the driver had to add the additives.From his gallon can,he put a slop in the first tank,a slop in the second and so on till he got to the last tank-it either got the remainder of the can or,more likely,zilch,the can was empty!
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Gosh! But that means that the base fuel is the same-and hence the calorific value of the fuel is the same-so no reason for more mpg.
Previous thread here, where I posted an explanation of what premium diesel does. Believe me or not, as you like. It came from a petroleum chemist who worked on the fuel standards (known personally to me, not a friend-of-a-friend).
www.honestjohn.co.uk/forum/post/index.htm?t=82275
In a nutshell, it's about keeping injectors clean, not calorific value. And you won't necessarily see any benefit at all, unless your injectors were dirty in the first place. The premium diesel fuels also have a higher cetane value (55 vs 51 for standard BSEN590).
What's the relevance of this to supermarket vs. branded? Additives make a difference. Supermarket, branded, and differently branded fuels have different additive packs.
I wouldn't try to dissuade anyone from using supermarket petrol, which might or might not be as good as a given brand. It won't generally be the same though. I choose to use Shell. It's as cheap where I buy it, and I get points, and I don't have to enrich anti-competitive supermarkets even more.
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Sorry, but this looks like a sleight of hand trick; the true part is that deposits in injectors will affect spray pattern and quantity, the deception comes from the allegation that 'ordinary' fuel is somehow more prone to causing deposits than premium fuel.
That's why I keep asking what these additives are and what quantities they are added in. For some reason the details remain sketchy. Why is the recipe such a secret when any of the competitors could easily undertake chemical analyses of rivals' fuel...?
I've already opined that cetane rating is a double edged sword and I'm sticking to that line. In some ways petrol works quite nicely in a compression ignition engine-you get virtually completely soot free combustion-precisely because the cetane rating is so low.
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I have found that when i drive on tesco unleaded i get a lower mpg as compared to shell unleaded. i know shell unleaded is more expensive but after all the calculations are done, the pound per mile value (how much it cost to drive a mile) is better when driving with shell unleaded.
i am currently experimenting with v-power to see if the pound per mile is better with it.
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Its all vry confusing wil we ever get a definite answer on this subject?
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Its all vry confusing wil we ever get a definite answer on this subject?
You never will, this is one of the most discussed topics on motoring boards, there is more myth and fokelore surrounding the old Supermarket vs Branded argument than you can shake a stick at.
My belief is that naturally all fuel in an area is supplied by the same distributiuon depot. However depending on who the base fuel is for, the tanker driver has a card which determines the additive pack required by a specific customer. I guess we will never know how this can vary.
Furthermore, I think petrol car drivers should not worry asa the spec for petrol is so exact compared to that of diesel so I would be amazed if there was truly any discernable difference between the two, and any performance/MPG issues would be more down to temperature/prtessure etc.
Diesel is a bit of a differnt ball-game, and not only can diesel vary from refinery batch to batch, or from different refinerys, the additive pack is capable of having a profound effect on noise, mpg and performance.
Having said all of this, I have never found a true difference between my local shell garage and any of the supermarkets diesel in Reading.
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My nearest Shell is always 1p a litre cheaper than the supermarkets so they get my business.
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I'm not sure it's deception! The build-up of deposits on valves and combustion chambers from "non-premium" fuel is quite well known. Bore-scope examinations in one of the mags are the only illustrations available to the public that I have seen. They have been cited here several times before. Other than that, the fuel standards people have been pressing for a detergent standard in fuel. "On behalf of automobile and engine manufacturers from around the world,we are pleased to present the Fourth Edition of the Worldwide Fuel Charter.The Charter was first established in 1998 to promote greater understanding of the fuel quality needs of motor vehicle technologies and to harmonise fuel quality worldwide in accordance with engine and vehicle needs. Importantly, it matches fuel specifications to the needs and capabilities of engine and vehicle technologies designed for various markets around the world."
Here is a link to my citation: tinyurl.com/3esx5d7 Page 34 gives an outline of the effects of deposits, and the reasons for additives. There are later documents re bio-diesel etc. It's not required at present under EN 590. So, it seems quite possible that long-term use of lesser fuels will lead to loss of performance and increased Nox due to unwanted deposits. As Manatee said earlier.
Edited by nortones2 on 17/05/2011 at 12:35
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Page 34 gives nothing of the sort! It gives an outline of the effect of cetane. There's nothing about deposits until p47-48-and then the report mentions (re injector fouling) "...At present, such a standardized test procedure has not been established...".
So they're convinced that fouling of injectors is a problem, but they haven't got managed to devise a test to measure the phenonemon?
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Terribly sorry I misled you on the page number. Maybe it was because I looked at it in Google rather than the usual pdf viewer. I do most sincerely apologise. Not. However, if you look at the section on gasoline engines there is information about deposits, their effects and remedies. There is a test for measuring deposits, and bearing in mind the report is several years old there may be newer tests specific to diesel engines. That being said, whether there is a test or not, the engine manufacturers and Bosch have flagged up problems and remedies to a known issue.
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Not that I would wish to "crow" or owt
But der ould Galaxy is still going like a clock after 234,000 miles of mostly non premium diesel i.e. rarely if ever Shell BP or branded expensive stuff.
Sometimes Supermarket or Maxol or "smuggled", but never filled at a "buckshee" or cowboy site. ( well just for a month or so)
& the Origional injectors seem to be fine,(& cannot know since they havney ever been pulled)
Ok in the -15 frost she gargled & spluttered a bit before coughing into life, but hey she started.
& her still be capable of astoundingly good mpg forby.
That is all
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I'm not sure it's deception! The build-up of deposits on valves and combustion chambers from "non-premium" fuel is quite well known. Bore-scope examinations in one of the mags are the only illustrations available to the public that I have seen.
I totally disbelieve this. It is one of these marketing concepts which is almost impossible to dis-prove and so in most peoples minds is in fact a fact !
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Sorry, but this looks like a sleight of hand trick; the true part is that deposits in injectors will affect spray pattern and quantity, the deception comes from the allegation that 'ordinary' fuel is somehow more prone to causing deposits than premium fuel.
There is no deception. In the case of diesel, "ordinary fuel" is more prone to producing deposits than premium fuel.
Ordinary diesel is a product of simple distillation of crude oil. Along with the selected long chain hydrocarbons (including cetane) that are captured come all sorts of other incidental compounds with a similar boiling point - these are the ingredients that create the deposits. Aside from the additive pack, the diesel superfuels like BP Ultimate and Shell V Power are predominantly GTL (gas-to-liquid) fuels synthesised from LPG - smaller HC molecules like butane are joined together to make longer chain HCs like cetane. The resulting fuel has less of the deposit-forming compounds so regardless of cetane rating is far less able to produce smoke and contribute to dirty injectors. GTLs are a more ideal fuel for diesels and remove the need for or benefit of extra fuel additives or cleaners.
So I have been given to understand - not my specialist subject, I merely pass it on from a reliable, first hand, source who himself considered these fuels worth the extra.
I appreciate this is slightly off the point of whether supermarket fuel is inferior, but I hope it is interesting and underlines the point that not all fuel is exactly the same.
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Ordinary diesel is a product of simple distillation of crude oil.
Gross GCSE chemistry style over simplification. There's a lot more to producing fuel than that.
the diesel superfuels like BP Ultimate and Shell V Power are predominantly GTL
A truely synthetic fuel would be eye wateringly expensive-think nitromethane or quality engine oil~£5/litre-before tax. Shell claim to use SOME GTL synthetic diesel-nowhere do they claim that Vmax is predominantly synthetic. I don't think BP claim to use GTL in their Ultimate diesel.
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I shouldn't have used the word predominantly - I stand corrected.
I don't believe it's meaningfully inaccurate to say common fuel oil is produced by simple distillation, but perhaps you'd like to expand?
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You're right about long, unbranched chains being desirable for compression ignition, and short branched chains being desirable for spark ignition.
Simple distillation would turn the barrel of crude into fractions of roughly the desired molecular weight-with a lot of waste. There are further processes: Cracking, unifiation (opposite of cracking) and Alkylation. Alkylation changes the structure of the molecules-which changes their chemical properties. This is important since trimethyl- pentane has the same molecular weight and empirical formula as n-octane but the branched structure has very different properties to the unbranched structure. Thus most of the original barrel of crude can be converted into useful fuels which could not be achieved via simple distillation. There are other processes to remove impurities like sulphur.
Interestingly, there is very little octane in petrol, and very little cetane in diesel. These species are simply used to arbitrarily define the autoignition properties of typical fuels.
After all, if making fuel was easy, we would all have distillation kits at home-and no one would buy taxed fuel!
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In an earlier post you claimed to get less mpg from supermarket fuel compared to Shell and the other majors. This is also my experience. Over the last 12 months I have done an average 2000 miles each month, repeating the same journey of 412 miles each working week with very little mileage at the weekends. Driving on unleaded I am very conservative, low acceleration, reduced breaking, keeping the engine in my 2004 Mondeo below 3000rpm. Generally I use an Esso station but on the occasions I have filled up with supermarket fuel I have noticed an approximate 10% reduction in mpg. A more controlled scientific study would be welcome.
Edited by Meyer on 03/06/2012 at 14:20
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I can't do the maths, my brain hurts. What is the balance, for you, between the extra fuel you use against the lower price you pay for it? All fuel meets the relevant British Standard but it is generally believed that the additives in the higher priced fuels made them worth the extra. Who knows?
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Not even the fuel companies claim 10% extra economy.
There have been lots of studies carried out by organisations such as the US EPA, SAE and even Which?. Virtually all of them reach the same conclusion. There is no statistical difference in fuel economy between different grades of fuel-especially for petrol or older diesel engines.
Is it possible that you're subconsciously changing your driving style when you fill up with a different fuel? If you do long journeys you should be able to achieve very consistant results. Get a friend to fill 'er up for you and then do a blind test!
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There is no statistical difference in fuel economy between different grades of fuel-especially for petrol or older diesel engines.
They should have asked me-when living in the UK and using a tankful of diesel a week I found it noticeable that fuel from my local Sainsburys gave about 5% -10% less mileage per tank than branded fuel so I tended to avoid using it. The cheaper price didn't compensate for the reduced fuel mileage.
During the time that I was driving to and from France prior to moving here I was running the tank low in the UK and filling up with cheaper diesel in France. Always got a dramatic jump in fuel economy as soon as running on french supermarket diesel. By dramatic I mean an increase from about 47 mpg indicated to mid fifties on the car's computer. It got so noticeable on our various trips over here that my wife could predict when the improved economy would kick in. Ok we all know that car computers are not that accurate, but as a comparison tool they are. And as soon as I returned to UK and started using uk fuel down went the fuel economy again.
I am of the opinion that the differences are due to the specific gravity of the fuel not additives, ie the more lighter fractions in the diesel the less dense it will be and the less energy per injected quantity, hence more has to be injected to achieve the same result etc etc.
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I am of the opinion that the differences are due to the specific gravity of the fuel not additives, ie the more lighter fractions in the diesel the less dense it will be and the less energy per injected quantity
This is quite correct-and always shows up in tests conducted with blended fuels containing methanol or ethanol. But there is limited leeway in changing the density whilst adhering to specified limits of aromatics, olefins and paraffins and physical properties like pour point, vapour pressure, flash point , T10 and T90 boiling points etc.
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