fixitagaintomorrow said:
Better reply - Perhaps it works better on tuned and superchipped engines, maybe mine is on the point of detonation and Optimax lets the engine work to its full potential?
Pete, You may well be right, but if we must have a theory, Here is the considered views of the sad guy who has actually done serious research into fuel composition and Oil company pricing and distribution strategies. Who even checks and records fuel consumption for every fill up.
Hopefully everybody will be entirely bored with this subject after reading this post
1: Octane rating has no direct correlation to the amount of energy in the fuel
2: Octane is measure of how much you can compress fuel before it spontaneously combusts. The reason that high performance engines need high octane fuels is not because the fuel has inherently more power but because they tend to use higher compression. The extra power comes from the higher compression not the higher octane. Higher Octane fuels actually tend to have less energy content.
See:
http://en.wikipedia.org/wiki/Petrol for a really good explanation
3: Fuel varies in its composition, petrol (or diesel) is a mix of many different compounds (see above link) the composition and the mix vary considerably from refinery to refinery, as the final product is dependent on the technology in the refinery (different cracking processes) and, more importantly the crude oil mix in the feedstock. They also produce different mixes of fuels for different temperatures to cope with vaporisation at different temperatures. So the Optimax you buy in summer is not exactly the same as the Winter version. This is because cars require higher volatility fuels at lower temperatures (so that your car will start in the cold but the fuel will not cause vapour locks in your fuel lines in the summer)
Because the main (but not the only) consumer regulation is about Octane or RON in Europe. Oil companies segregate their market on the basis of RON. The price we pay is really nothing to do with the cost of production. Higher performance cars tend to be more expensive and have drivers that are willing to pay a higher price, so historically oil companies charged us more for higher RON fuels.
This is because we are prepared to pay more or have to pay more if we have a high compression engine. Not because the fuel is better or more costly to produce. For oil companies it’s a great way of increasing margins by selling a slightly modified product to a market segment that is prepared to pay more. Much more profitable, lets say, than adding a bigger engine, alloy wheels, and better brakes, a stereo, and a badge, to a car. To sell to a customer that is prepared to pay more for better performance, or comfort, or kudos.
The energy content in a fuel varies from manufacturer to manufacturer and refinery to refinery, and month to month, dependent on the mix of crude oil used in the feedstock. It is possible that the optimax that you have been using has been using has an intrinsically higher energy content. This would give more power and require less fuel to give the same speed, not because of the RON but because the mix of different compounds. It also may be the case that Optimax as well as having a higher RON has intrinsically higher energy content because of the mix of hydrocarbons and perhaps Shell have better quality control over the formulation of the petrol.
I somehow doubt the last point or they would make more of this in their advertising, which this seems to centre on the implication (but not a claim or factual statement) that Ferrarri use optimax in their F1 Cars.
Oil companies do not use energy content or genuine performance measures in their marketing for three reasons:
1. They don’t have to - they can segment the market using RON and get greater margins courtesy of the regulation system. Its much easier to maintain quality control around RON values by varying the addition of high RON compounds or additives, than it is to guarantee the energy content which is much more dependent on the crude oil feedstock and the refinery technology.
2. Quality control over energy content is difficult, as storage conditions and time in storage affect the exact mix of compounds delivered to your fuel tank. Also their manufacturing processes and the mix of crude oil they use to keep their costs as low as possible make this difficult. The mix of crude oil depends on their stocks, the price on the spot market and their mix of oil futures contracts. (some of the crude oil they pump out of the ground themselves, they buy some from other oil companies, and some from the spot markets and futures markets for crude oils)
3. Their distribution systems mean that it is difficult to produce exactly the same (or even similar in performance terms?) product in say Newcastle that they do in Bristol. Different refineries using different crude mixes and different technologies are simply not capable of producing a homogeneous product . They also like the flexibility to blend their fuels using some petrol bought on the spot market if the price is favourable, another major variable to the exact fuel content
When I was into racing 1/4 scale model cars most of the better drivers used Texaco from a particular part of the country as the mix of hydrocarbons and additives produced a fuel with more intrinsic energy. The fuel had been tested extensivly by a top Karting team. If I remember correctly it had a significantly higher benzene content than the other fuels. However after about 6 months the mix changed and the fuel was actually worse in performance terms than many others. The Karting team and most of the top drivers moved on to a fuel from Elf stations again as a result of extensive testing. The fuel was not quite as good as the previous Texaco mix but better than most others. At this point rules were introduced to prevent this as it favoured a group of drivers that lived in a particular part of the country, and we all had to use fuel provided by the organising scrutineers. Which meant different fuel mixes is different parts of the country but everybody had the same stuff.
This is an interesting read about fuel performance from an American site:
http://www.idavette.net/hib/fuel/
As I said in my previous post the only way to know if one fuel is better than another is to test it in reasonably controlled circumstances (mainly driving style and types of roads). If you get better fuel economy consistently with one brand or even one particular filling station then it’s probably better. But don't be fooled by Octane or RON. This has absolutely nothing to do with performance or fuel economy.
But also remember that the fuel sold at the pump is very variable in almost everything but the Octane or RON and perhaps the mix of detergents. The fuel you buy today will be different in a few months time even if it’s the same brand from the same filling station. The same brand fuel is also very different in different parts of the country, as it will come from a different refinery and through a different distribution system. It may or may not have similar performance characteristics.
Maybe everybody will stop arguing about this if they know a little more about it, I hope so as I'm bored with it and as you can see I can bore for England on this subject.
Regards,
Michael
