Shell V- power
Discussion
Seems some people are looking at this the wrong way round.
You don't gain anything by using 98 or 99ron fuel in an engine designed and tuned to run on the stuff, rather you get less power if you put the wrong fuel in.
Detonation occurs > sensor is triggered > ECU retards ignition timing = less power. As kayc has observed, the reduction can be dramatic with a turbocharged engine.
Running an engine designed and tuned to use 95ron fuel on 98ron fuel will make negligible difference, but will cost more.
So what of some of the other claims for Optimax? It's denser and carries some oxygen of its own.
Can anyone post the specific gravities of the various brands available in the UK?
Does anyone know how much oxygen is available in the fuel?
How much of this extra “density” is other (non power producing)additives? I'm not doubting these claims, I'm genuinely interested in the data. Assuming there is a significant difference over other premium fuels, then there should be some extra power available providing (and this is the catch) the engine is specifically mapped to take advantage of the fuel.
(BTW. A lot of carburettor equipped motorbikes run very poorly on Optimax and a significant density difference would explain why)
What about the additives package, cleaning your engine as you drive?
I’m trying to imagine a modern fuel injected engine with the combustion chambers full of carbon and dirt streaked all over the backs of the inlet valves. So much carbon that the compression ratio is raised and with the hot spots caused by the carbon as well, the engine is prone to pre ignition or detonation. Introduce your wonder fuel and as if by magic the carbon disappears and normal service is resumed.
So how does the engine get so dirty? Where does all the dirt go? Into your oil or through the CAT? There has to be some cleaning effect (or some idiot would have sued Shell by now) but it’s hard to imagine it being more effective than a proper top end overhaul.
It’s also hard to imagine a modern engine getting in such a state without also developing more urgent and power sapping faults.
Optimax is good fuel, but so are all the other brands of 98ish Octane fuel. There may be differences, but they are very small. Personally I use the correct grade of fuel, maintain all my cars to a very high standard and enjoy them, without worrying about plotting a course from Shell station to Shell station around the country. It simply doesn’t make enough difference to be worth worrying about.
You don't gain anything by using 98 or 99ron fuel in an engine designed and tuned to run on the stuff, rather you get less power if you put the wrong fuel in.
Detonation occurs > sensor is triggered > ECU retards ignition timing = less power. As kayc has observed, the reduction can be dramatic with a turbocharged engine.
Running an engine designed and tuned to use 95ron fuel on 98ron fuel will make negligible difference, but will cost more.
So what of some of the other claims for Optimax? It's denser and carries some oxygen of its own.
Can anyone post the specific gravities of the various brands available in the UK?
Does anyone know how much oxygen is available in the fuel?
How much of this extra “density” is other (non power producing)additives? I'm not doubting these claims, I'm genuinely interested in the data. Assuming there is a significant difference over other premium fuels, then there should be some extra power available providing (and this is the catch) the engine is specifically mapped to take advantage of the fuel.
(BTW. A lot of carburettor equipped motorbikes run very poorly on Optimax and a significant density difference would explain why)
What about the additives package, cleaning your engine as you drive?
I’m trying to imagine a modern fuel injected engine with the combustion chambers full of carbon and dirt streaked all over the backs of the inlet valves. So much carbon that the compression ratio is raised and with the hot spots caused by the carbon as well, the engine is prone to pre ignition or detonation. Introduce your wonder fuel and as if by magic the carbon disappears and normal service is resumed.
So how does the engine get so dirty? Where does all the dirt go? Into your oil or through the CAT? There has to be some cleaning effect (or some idiot would have sued Shell by now) but it’s hard to imagine it being more effective than a proper top end overhaul.
It’s also hard to imagine a modern engine getting in such a state without also developing more urgent and power sapping faults.
Optimax is good fuel, but so are all the other brands of 98ish Octane fuel. There may be differences, but they are very small. Personally I use the correct grade of fuel, maintain all my cars to a very high standard and enjoy them, without worrying about plotting a course from Shell station to Shell station around the country. It simply doesn’t make enough difference to be worth worrying about.
flemke said:
ballcock said:
Be happy!! .. When you get down to the nitty gritty of the small print , Shell V power in Ireland is a paltry 95 octane ..
But it's still about 8p/l more than 'unleaded 95' ... Feckin rippoff!!
So is there no "super premium" octane available there? But it's still about 8p/l more than 'unleaded 95' ... Feckin rippoff!!
Are you saying that you can only procure standard "premium" with 95 RON, but they call it "V Power"?
Yes Flemke , if you check the Irish shell site , they admit (in very small writing!!) that it's only 95 ..
Brady had told me of one or two places that do 97 , but he didn't mention if they were the 'poop' fuel places ..Is the Place on the Naas road ok for fuel Brady??
simonharrod911 said:
Willibetz and nick_968 both seem to put convincing arguments, but they contradict each other. Any other comments? I'm particularly interested because my standard GT2 seems to drive identically on 95, although it's the first Porsche I've had that doesn't seem to benefit from better fuel.
Edited by simonharrod911 on Wednesday 25th October 16:36
Thank you. As for further comment, I'd just reiterate that I'm correct
That's not to say that nick_968 is incorrect. Without wishing to presume his meaning, I think we were making slightly different points.
I was discussing severity of operation - how hot and pressured things get in the combustion chamber, which influences an engine's octane requirement.
nick_968 made the point that stress has a specific and different different meaning in this context, and correctly points out that air temperature will influence performance (Humdidity will too). He also suggests that an engine tuned to run on 95 RON fuel will run on 95 RON forever without problem, which is essentially correct if we ignore the tendency for the octane requirement of an engine to increase with age (a phenomenon caused by carbon deposits and known as octane requirement increase).
Hope that helps,
WilliBetz
Didn't Top Gear magazine do some test on these premium fuels? IIRC there were significant differences in the bhp achieved with the same car using different fuels. Tesco's premium fuel actually got some very good marks...
Just looking at Octane level is misleading as the additive package also has quite some impact both on performance as well as MPG.
Just looking at Octane level is misleading as the additive package also has quite some impact both on performance as well as MPG.
mtbr said:
Running an engine designed and tuned to use 95ron fuel on 98ron fuel will make negligible difference, but will cost more.
Unless you are running a car with cat and lambda feedback, and the higher octane fuel is oxygenated (increasingly common in super unleaded fuels).
Then, in order to maintain stoichiometric combustion, the injector open duration will increase, you'll burn more fuel and generate more oomph.
WilliBetz
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