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Went to fill up earlier and optimax has gone over ?1 per litre. So I was just wondering how many people luike me are thinking of switching over to normal unleaded, and how many people already use unleaded and think it is fine and no harm will be done to the car.
 

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You forgot the "NOw use other supplier's fuel above 95 RON". So I haven't voted [:)]

I had a serious word with the old dear who co-runs my local shell after being stung 101.9 (4p rise in a couple days, 4p over the diesel price now, which is outrageous). She thought I was having a laugh until I proved she was more expensive that the other kinda local shell - who are renowned for being SERIOUSLY over priced.

WOn't be back there for a while. Will end up crossing between Tesco's 99 and Esso's 97 now, as both are normally reasonably priced.

C
 

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I'm still using Optimax no matter what.

Even if I switch back to unleaded, it's only a small matter of time before it rises to Optimax prices. Thats the way I look at it.

I'm just paying tomorrow's normal unleaded prices now (if that makes sense)
 

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101.9 ??? That's nothing. One of the garages near me is charging 106.9. Daylight robbery.

These prices are quite annoying too as I have a lambda sensor on the blink and the last thing the R needs is 95 RON. It's driving bad enough as it is.
 

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I use that site too, really useful.

My local shell is selling optimax at at 104.9, but the next shell is only at 101.9, so it pays to use the site!

I really can't find a Rhyme nor reason for the Optimax prices, they seem to rise and fall independent of 95Ron, and independent of other Shell garages.
 

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During a recent business trip to <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:eek:ffice:smarttags" /><st1:country-region><st1:place>Germany</st1:place></st1:country-region>, I visited a well know German race engine tuner, who had a state of the art rolling road and ECU programming business.

I asked him if hi octane pump fuel made any difference to power figures. To which he answered none what so ever.

He said higher octane just allows the engine to run slightly more ignition advance, which helps emission levels.
 

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During a recent business trip to <st1:country-region><st1:place>Germany</st1:place></st1:country-region>, I visited a well know German race engine tuner, who had a state of the art rolling road and ECU programming business.

I asked him if hi octane pump fuel made any difference to power figures. To which he answered none what so ever.

He said higher octane just allows the engine to run slightly more ignition advance, which helps emission levels.
EVO did a test the other month with different fuels followed by RR runs on 3 different cars, and the fuels DID make a difference.
 

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He said higher octane just allows the engine to run slightly more ignition advance, which helps emission levels.
That's true, but the knock on from advancing the timing and running the engine more efficiently is that you can extract more power. In order to run at high revs safely, you need a high octane petrol to prevent detonation from occuring. For instance, if you stick crap petrol into a Honda S2000, the ECU can decide that the fuel isn't suitable to prevent detonation occuring at very high rpms and will therefore prevent the VTEC cam change from occuring.

To say that high octane petrols make no difference is ridiculous. If this was the case, racing cars would just grab some fuel from the local Tesco. If you want to see what difference octane makes, just try pouring some toluene into your tank to raise the level and once your ECU has adjusted, you'll have a bit of a shock.
 

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He said higher octane just allows the engine to run slightly more ignition advance, which helps emission levels.
That's true, but the knock on from advancing the timing and running the engine more efficiently is that you can extract more power. In order to run at high revs safely, you need a high octane petrol to prevent detonation from occuring. For instance, if you stick crap petrol into a Honda S2000, the ECU can decide that the fuel isn't suitable to prevent detonation occuring at very high rpms and will therefore prevent the VTEC cam change from occuring.

To say that high octane petrols make no difference is ridiculous. If this was the case, racing cars would just grab some fuel from the local Tesco. If you want to see what difference octane makes, just try pouring some toluene into your tank to raise the level and once your ECU has adjusted, you'll have a bit of a shock.
Your confusing racing fuel additives with Forecourt pump fuel and marketing PR.

You can?t compare a proper full race engine with blended fuels, especially designed for a racing engine with 98 octane pump fuel.
 

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I wasn't considering full-on race fuels, give me some credit. The stuff that the various international motorsports use is generally produced in a lab, by men in white coats with beards, in small quantities.

The most common mistake is that a high octane petrol "contains" more power than a standard fuel. This is not true. The octane rating is basically a measure of a fuels ability to resist knock and detonation not how much power it can give out. However, this ability to resist knock can be used to produce more power.

Modern engines run at higher and higher compression ratios and advanced timing in order to (as you said) help emissions levels. In order to achieve these compression rations and timing settings a high octane petrol must be used in order to prevent the aforementioned knocking (pinking) and detonation from happening. So, when you turn up with one of these cars and chuck in some 95 RON fuel, the ECU will detect this and retard the timing so as to prevent any damage from occuring. The resultant effect of this is that the car will run outside of it's recommended parameters and affects MPG, emissions.....and power produced.

Ignoring that all that, just check out some independant tests that have been done on fuels. Evo ran a test a few months back (using a GTI none-the-less) and showed that the higher octane fuels produced more power.

At the end of the day, this is one of those touchy subjects that there will always be two sides to !!
 

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I'm still using Optimax. The price at my local Shell is 104.9 but the few pennies here and there mean what max 10p per litre so full tank is gonna be ?5!

2 tanks a month, so around ?120 a year potential saving if moved to normal UL.

Do I care? Nope. I love my GTI.

I'm even considering giving BP Ultimate 102 a go at ?2.40 a litre!!
 

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I've switched to using Tesco's Ultra Low Sulphur since the first recent price hikes sent Optimax over ?1 per litre. Now I openly admit, I'm not a tuning specialist or mechanic so any subtle differences in performance are going to be beyond my scope of analysis but I've been driving for 28 years and am pretty seriously into my cars. I honestly have not noticed any significant difference in performance or fuel consumption since the switch. The car seems to run just as smoothly and accelerates just as well as it did with Optimax.

If I could notice the difference, I'd go back to Optimax but I can't so don't see the point.
 

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I?d like to see these EVO test result, I doubt there ability to reproduce the test results in an accurate way, did they use the same car and run them on the same rolling road with the same ambient temperature and barometric reading?

Going from 95 to98 octane will not produce more power, what it will do is burn cleaner combustion, and as you state allow for more ignition advance, which in turn with aid better throttle response. The effects on a turbo engine will be greater than a normally aspirated engine (which is relevant to this forums members)

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p> </o:p>

Being in the industry has over the last 25 allowed me the luxury of talking to many engine tuners for both road and track, these some of these Guys are the best in there field, Chip tuners find it almost impossible to extract more power from N/A engine as all modern chips can do is dial in a little more ignition advance.

<o:p> </o:p>

I?d have yet to meet a driver who can detect a gain of + 10 BHP when driving a car with around 150 BHP, it?s a bit like a noisy exhaust, you physiologically think you have more power.
 

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I'm still using Optimax no matter what.

Even if I switch back to unleaded, it's only a small matter of time before it rises to Optimax prices. Thats the way I look at it.

I'm just paying tomorrow's normal unleaded prices now (if that makes sense)
That makes sense. The point is, how many of you all are paying for your petrol/diesel out of your 'own' money as distinct from your company's expenses or having your petrol paid for you by the company with whom you are employed?

I know that my, admittedly small (by comparison), annual mileage has to be funded by my company and state pensions!!

[:(]
 

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During a recent business trip to <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:eek:ffice:smarttags" /><st1:country-region><st1:place>Germany</st1:place></st1:country-region>, I visited a well know German race engine tuner, who had a state of the art rolling road and ECU programming business.

I asked him if hi octane pump fuel made any difference to power figures. To which he answered none what so ever.

He said higher octane just allows the engine to run slightly more ignition advance, which helps emission levels.
Remind me not to take my car there to be tuned because from what you just said, he knows absolutely f*ck all!

As Spanner says, the one and only reason for using a higher octane fuel is to prevent detonation. I can't believe someone would be so stupid in thinking that a higher octane fuel dmakes no difference to power figures! Of course it does.

Try putting some 91RON in a Golf Gti, then some 98 RON and I'm sure you'll see the difference! The reason you need higher octane fuel in cars like the Golf Gti and Honda S2000 is because they have high compression ratios. The Honda is something like 13.5:1, the Golf is about 10:1 which is very high for a forced induction engine, as with boost pressure, the effective compression ratio increases.

Modern ECU's sense when detonation is occuring and retard the ignition to try and prevent it therefore decreasing the power output. I think the Golf Gti is probably on about the limit.

So running an engine with a low compression ratio on 98 RON isn't going to make any more power, because detonation wouldn't occur if using 95 RON. However, in something like the GTi, detonation probably would occur with 95 RON and the ecu would retard the ignition to try and prevent it, therefore using 98 RON would allow you to run the original advance intended, not more advance.

In summary, a higher octane fuel allows a higher compression ratio or effective compression ratio and hence more power.

The power difference will be more noticable in forced induction cars, especially ones that have had their boost pressure (and hence effective compression ratio) increased. There aren't that many normally aspirated engines that would benefit power wise from 98RON fuel, Honda Civic Type R and S2000 are two examples I can think of. Some people say the FSI VW engines are meant to run on 97 or 98 RON but I doubt there would be any power difference in such an engine.

The only reason for doing it, as somebody has pointed out, is to prevent detonation due to high combustion chamber temperatures.

Nick
 
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