There was a thread which touched on quality of fuel etc, and the nub of an argument was cited in my last response. Can't now find this thread which possibly has been removed editorially! Since then I have had a helpful response from Shell:
"Combustion in an engine will always result in carbonaceous deposits being formed. There may also be issues with oil leakage which can results in further deposits on combustion. Engines run on stop start cycles will be much more prone to deposit build up than those run continuously over long periods of time (probable explanation for the test bed comment). Most major motor manufacturers now recommend detergent fuels. Specific references you may find interesting:
LM Gibbs, Chevron Research & Tech: Gasoline additives - when and why SAE paper 902104
GT Kalghatgi, Shell Research Ltd, Deposits in Gasoline engines - A literature review SAE paper 902105 (This extensive paper describes not only deposits and where they form, where they come from and their harmful effects, but also how they are controlled)
MJ Papachristos et al of Associated Octel, fully synthetic gasoline additive packages to meet the needs of the 90s. SAE paper 932809 "
Unless there is further interest/argument with the papers cited by Shell, I am satisfied that there is merit in only using fuels with a claim to quality.
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All papers produced by independent third party university research departments; not funded by major oil producers; fully peer reviewed? I think not!
Tescos it continues to be for my gas guzzler.
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I'd be glad to see those papers which say you don't need to control deposits.
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I'd start by tracking down the papers to which they do refer, and seeing what (if any) conclusions they draw. My scientific training suggests to me that the letter is some standard flannel, wheeled out to bamboozle the innocent punter.
It all sounds very impressive but there's nothing in the titles of the papers that concludes one way or another. There is a literature review which is bound to be fairly biased towards petrochemical industry papers. The most damning evidence, (and I'm just restraining myself from putting this in capitals) is that their email makes no reference to the proposition that detergents are a good thing!
I don't doubt for a moment, Nortones2, that deposits are a bad thing. But read their weasel words:
"Combustion in an engine will always result in carbonaceous deposits being formed. [ok] There may also be issues with oil leakage which can results in further deposits on combustion. [fine] Engines run on stop start cycles will be much more prone to deposit build up than those run continuously over long periods of time [I dare say] (probable explanation for the test bed comment). Most major motor manufacturers now recommend detergent fuels [so what. why? because they are in league with Shell? Or because they've done research. I know what I think...] Specific references you may find interesting [but far from informative]:
LM Gibbs, Chevron Research & Tech [who are they? don't sound very independent to me]: Gasoline additives - when [not] and why [not] SAE paper 902104
GT Kalghatgi, Shell Research Ltd, Deposits in Gasoline engines - A literature review SAE paper 902105 (This extensive paper describes not only deposits and where they form, where they come from and their harmful effects, but also how they are controlled) [and in fact makes no reference to detergents at all other than in papers produced by the industry???]
MJ Papachristos et al of Associated Octel, fully synthetic gasoline additive packages to meet the needs of the 90s. SAE paper 932809 " [conclusion the need is minimal???]
Snakeoil all round?
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And in fact, read that 'helpful' bit after the paper, in brackets. It makes absolutely no reference to the superb power of (the detergents which are used in) Shell Optimax to counter this build up. If it did make such a reference, then I've no doubt that it would be on all their advertising literature!
>>GT Kalghatgi, Shell Research Ltd, Deposits in Gasoline engines - A literature review SAE paper 902105 (This extensive paper describes not only deposits and where they form, where they come from and their harmful effects, but also how they are controlled)
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I know the subject of fuel quality has been covered a lot but from my experience with buying diesel the following outlets seem to suit the car the best (the best at the top)
Shell Diesel Plus/Extra or whatever they call it
Shell (regular)
BP
Esso
I did fill up from a much smaller international retailer and had awful performance and economy.
I am still reluctant to spend much more on the BP Ultimate.
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Well, it may be that Tesco fuel has additives, in which case you may have found the holy grail. Good for you. However, I haven't yet read these papers, if I can get hold of them, but see no reason to suspect, a priori, that they are whitewashes. Perhaps you could cite the counter arguments rather than rely on sarcasm?
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Hang on, many apologies if you think I was being sarcastic. I certainly wasn't trying to be, and should hate to think that you think I was. Sorry. Very sorry.
The drift of my line was that their 'evidence' was downright flaky, at best, and at worst, not evidence at all. Quoting the titles of some papers written by the Shell research department isn't exactly convincing, is it!
I mean, really, it isn't, is it?
It's not that the papers are whitewashes, just that they will be written from a particular slant. If nothing else, the researchers will want to continue to justify their funding, so will have looked long and hard to find something that will please the hand that feeds. That is not to say that they will lie, but they are hardly impartial!
The letter from Shell is a complete whitewash. It contains no evidence, points to no evidence, and is completely unhelpful! All it does is refer to the titles of a couple of papers.
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It's not even a matter of argument & counter argument.
There is a 'fact', peddled by Shell, that Optimax produces an x% better fuel economy, burns better & etc. etc. etc. The downside to using Optimax is that it is 10% more expensive than anything else.
In order to persuade me to pay a large premium in order to use Optimax, it will take more than an advertising campaign, that bats around non-specific claims.
IIRC a petrol company in the States has been prosecuted by their advertising standards people for making claims that it cannot substantiate - no doubt somebody will point us in the right direction.
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If I were in the Shell marketing department, I would want to be able to produce a brochure that says 'Cambridge academics say that Optimax helps your car'. As it is, they rely on hand waving vague arguments without any obvious foundation.
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So let me see then
That would be one paper written by a guy who works for Chevron,
One written by a guy who works for Shell
and one from Associated Octel. Who they? Associated Octel used to make the lead additions to petrol, who suddenly switched into detergents when petrol went lead free. Who do they supply? why Chevron and Shell.
Another litre of Tesco castor oil for you Laguna my lovely, you know its just as good as any other.
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Perhaps you could cite the counter arguments rather than rely on sarcasm........................ :)
Knew I'd heard of AO somewhere...
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My understanding is that Shell are allowed to advertise improved performance with Optimax as it is a higher octane rating than "premium" unleaded. It is a scientific fact that certain engines will produce more power with higher-octane fuel.
So, in this debate i think we must separate clearly between higher-octane fuel and its relevance in many road car engines, and fuel additives other than octane enhancers.
I am in no doubt that higher octane fuels are beneficial in *some* road car engines.
However I am sceptical as to the benefits of additives in fuel of similar "grade" (e.g. two brands of premium unleaded).
Aprilia has stated in a previous thread that since the imposition of a British standard in the mid nineties (EN something) detergent properties of all fuels on sale are now adequate.
So I ask, do people here think additives in Shell fuel for example are better, but irrelevant, as all others are already adequate?
Or, do people think, for example, Shell detergents are just as good as any body else?s?
I believe if there is benefit from Shell additives it is not likely that people who post here, with well-maintained vehicles, would benefit most.
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Thanks Aprilia, you have answered some of my questions even before i finished typing them!
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I am no expert in this field.but I have doubts about detergents being used in combustion process ie unless detergent is burnt it hangs around in the chamber/bores valves which unless I am wrong would mean it would after heavy revving get caught in the piston rings causing the seal being the oil to break down.which would then follow slight compression would be lost.and as I am not aware of any detergent that is capable of removing carbon I cannot see how it would benefit.it would though help in burning any excess oil that is being transmitted into bores.maybe that is what its for?
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Mech1
Fuel detergents are basically surfactant chemicals that allow the fuel to 'wet' the metal surfaces of the fuel system. The solvent action of the fuel then removes the deposits.
Detergents used to be important because fuel contained quite high levels of gums and 'heavy end' petroleum. This could build up in carburetor jets and around injector pintles. The detergent allows the fuel to dissolve away these deposits.
Modern fuels contain very low levels on contaminant so detergents are much less important - but I am not aware of any UK retail fuel that *doesn't* contain some detergent. You can buy non-detergent fuel, but it is for use in combustion reseach, engine development etc.
Agree with the point earlier about RON of Optimax being higher and of benefit with engines can than make use of higher RON.
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I am not convinced by the argument that all fuels are treated with detergents. And although the argument seems to be true true re heavy ends and gums, that is not the whole story, as I understand it. Anyway, here's enjoyment.independent.co.uk/low_res/story.jsp?stor...6, so, folks, you can still get cheapo fuels to misfire on!
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The quality of fuel additives varies tremendously it is a cut throat business and most fuel companies use a keep clean dose rather than a clean up dose, and use the cheapest available.
I assume the shell and BP optimax and ultimate use the very best detergents as well as using more "cleanly refined fuels"
(more oxygentes).
Good fuel additives do work, I have seen the results from field tests injectors stay clean and more importantly inlet valves remain clean.
Poorer additives with less thermally stable detergents may not keep inlet valves clean, an example we were always quoted in the additives industry was that the inlet valvws stems of a merc ran at about 200C, The slimmer valve stems of a Polo run at about 400C. Most detergents (amines) cannot withstand that temp.
Also compared to fuel with no additives treated fuel increases culinder head deposits by 10%.
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Optimax, with its RON 99 rating, will benefit certain high performance cars that benefit from the higher octane rating.
Most (the vast majority) cars will obtain no benefit from the higher octane available from Optimax. For your Polo, or your Astra, your Mondeo or your Granada it is just snake oil!
Those of you putting Optimax into 'ordinary' cars will be subsidising the distribution and marketing for the tiny fraction of drivers of cars that run better on 99 RON.
Again, I am sure that it is possible to configure a 'better' fuel, with maybe higher quality detergents that could make an engine last longer. But how many people run a car from new to 300,000 miles? (Much as changing the oil every 3k and 3 months may improve the longevity of a car,) you're only improving it for the next-but-three owner of your car.
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WRT this topic, what is a knock sensor - do ordinary cars have one?
Does this change ignition timing according to fuel RON rating?
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