Having been reading a thread regarding the benfits or not of using higher octane fuel. I've done a lot of searching and research on the subject. I've searched for the previous thread but can't find it!

Results from my research show that the higher octane fuels are superior in both performance and mpg despite certain commentators stating that you don't benefit unless the engine is tuned. Both fuels are designed to run on standard tune engines - the fuel burns more clean and therefore improves fuel burn efficiency and hence giving the results predicted.

I personally found a general improvement both in my petrol car and now my deisel car - the engine runs quieter with high octane fuel. Does anyone else have any similar experiences they would like to share on a public forum to quell the detractors Popular forums for bikes and cars; that prefer a fuel state that the fuel is different and not a merely a marketing ploy.

I'm just waiting for an answer back from our Technical Department to hopefully put this myth where it belongs -

On my turbo'd Corolla I noted the following from comparing fuels.

95 octane fuel = 215BHP
95 octane fuel + octane booster = 225BHP
Optimax = 230BHP

The ecu was having to retard ignition on 95 pump fuel as detonation was detected. The torque curve was also much smoother on the boosted fuels. On the road this meant the car was more responsive and smoother to drive.

All tested on the same rollers.

I believe the cleaning properties of Optimax are well documented and proven by independant magazine tests.

Justin

[Edited on 17/10/05 by bimbleuk]

Our Technical Dept. has just got back to me - they verify that the higher octane fuel's do improve performance, mpg and emmissions with no alteration of tuning. This is due to the cleaner characteristic's of the the fuel in question.

Oh BTW - my Technical Department is NGK Spark Plugs (UK).

Good news - having seen decent benefits on my MX-5, I've never even thought abouot running the Indy on anything but Optimax/Ultimate.

I also read in one of the mags that Tesco are supplying a 99 octane fuel from some of it's sites?!

I noticed today that my local Tesco is selling 99 octane Ultima or optima or whatever it's called but i'm too stingy to buy it!..... mind you if it does more mpg then perhaps it's not as expensive as it seems.

Hellfire, How much better is using high octane fule in a "normal" engine than using "normal" octane fuel? Did your technical department suggest how much this might be?

I'm interested in this as I will be going to SVA soon and want my carbed R1 to pass emmissions first time. If high octane fuel will make a difference then I will use it, at least for SVA.

Are there differences between manufacturers as well? I had an Escort 1600cvh when unleaded was introduced and as it already had hardened seats I altered the timing and spark retard valve as in the manual and ran it solely on unleaded. It would pink and splutter like a b@&tard on Texaco fuel but was fine on any other. I use octane booster in my pinto locost and I know that makes a difference, it pulls a lot cleaner and from lower down the revs.

Good point.....we have, in our business, been over the years, actively researching this very point.
We have been racing and preparing historics since for ever, but in 1999, it got more serious as in doing the Top Hat series, Gold Cup, Le Mans Classics, Le Mans Legends etc in 1950's Jaguars. Lead free conversions done to most of the engines BTW. The engines re-built by us.
I am happy to confirm that the cars absolutely flew at Le Mans. We had to use their fuel supplied by the Le Mans circuit, which was 100+ octane. All of the old cars we have re-built engines for, we insist use Shell Optimax......and in an emergency BP Ultima, the owners of the cars are very happy. The engines are also very happy.... .
I went on to try out Optimax in my modern tin top, it did not like it, it obviously didn't need such a high octane, it kept pinking.

For my 7 which has a 1978 cross-flow engine, lead free conversion, re-built by me, I use Optimax, it is also a very happy fozzmobile, and runs beautifully.

So, my experience tells me, that pre-moderns love the higher octane of Optimax, modern technology, does not.

I don't think that I would personally use the cheaper petrols a la Tesco Sainsbury et al, as I am unsure of their country of origin/purity. My take on it is, that if your engine is of the old variety, you have spent money on the re-build, it makes sense to use the best fuel available. But, all of the above is only my opinion, and our 'findings' of testing!

Fozzie

[Edited on 17/10/05 by Fozzie]

My x-flow is the same as yours, Fozzie - I feed it Optimax, as ordinary unleaded makes it run on when I turn off the ignition, even if I adjust the timing.

With Optimax, it runs well with no sign of pinking, even though the ignition was advanced a bit above 'book settings' at a recent rolling road session.

David

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Originally posted by David Jenkins
My x-flow is the same as yours, Fozzie - I feed it Optimax, as ordinary unleaded makes it run on when I turn off the ignition, even if I adjust the timing.

With Optimax, it runs well with no sign of pinking, even though the ignition was advanced a bit above 'book settings' at a recent rolling road session.

David

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I had a Rev3 MR2 Turbo, these run an electronic waste gate so boosts until the engine knock sensor backs it off. With optimax it managed 0.4 bar more which made quite a difference, 240 up to 270 bhp !

Fastest excellerating car I have ever owned, my BEC should trounce it when completed !

Cheers Mark

I think it depends on the question asked to your technical advisor

Firstly I believe the original question was whether 95 or 98 octane is best for an R1. With a suggestion that 98 RON will produce more power, mpg and cleaner emissions.

Please note the info below come from a number of sources and phrase it better than I can :-

Octane rating is a measure of how resistant the petrol is to premature detonation (knocking). Using a fuel with a higher octane lets an engine be run at a higher compression ratio without having problems with knock (Hence some real advantage for forced induction cars).

In simple terms compression is directly related to power, so engines that "require" higher octane usually deliver more power.

Some high-performance engines are designed to operate with a compression ratio associated with high octane numbers, and thus demand high-octane petrol. But most major manufacturers design on the basis of the fuel commonly available. High compression engines can be run on lower octane fuel by retarding the ignition with slight loss of performance.

The goal, then, is to find a fuel with an octane rating that is high enough to prevent knock, but not much higher.

Some people believe that adding a higher octane fuel to their engine will increase its performance or lessen its fuel consumption; this is mostly false—engines perform best when using fuel with the octane rating they were designed for.

Agree with the above,

Bike engines generally run a higher compression ratio than car engines and so would have been designed to run a higher octane fuel to prevent detonation. An R1 will almost certainly be best run on 98RON.

In turbocharged cars with electronic boost control, as was mentioned previously, the boost can be increased by the cars ecu until detonation is sensed by the knock sensor and then the wastegate is actuated. In my Fiat Coupe 20v Turbo this was evident at the Nurburgring filling up with the evil smelling 105RON stuff they had at the local filling station.

As for the cleaning ability of higher octane fuels I dunno...maybe the addition of higher levels of Benzene to slow the burn has the side effect of cleaning the fuel system to a greater extent?

In the diesel engine you mention, is it a turbo diesel with electronic boost controller?

Geoff

High octane goes with high compression, yes but isn't this thread looking at it from a different angle?

Different fuels burn at different speeds and different fuel compositions burn more completely (cleanly) under different conditions. Given this, if you run optimax / ultimate in an engine that is happy on 95 RON fuel, will the use of certain higher profile fuels burn more cleanly or efficiently?

I can imagine a scenario where a "good" fuel burns ideally in my engine as it is, giving lower HC and particulate levels than a "cheap" fuel that doesn't fully burn under the same conditions. Theoretically, the fully burnt fuel may release slightly more power for the same quantity of charge. This may lead to slightly better MPG as you don't have tp put your foot down as far to get the required power to maintian your speed. I can imagine this and I can imagine an expert running a series of experiments and proving it. Is the improvement 0.05%, 0.5% or 5%?

Technically - all engines differ.

Increases of lead in fuel aid's lubricity but reduces the speed of burn. Therefore, the time it takes to burn the fuel occasionally overlaps with valve opening and let's unburned fuel into the exhaust system, so loosing 'some' power - higher octane fuels increase the speed of burn thereby increasing the efficiency. Therefore higher revving engine's will especially benefit from this improvement. There have been no conclusive test's with NGK to state this as fact due to the first statement... and research into this would give very erratic results.

One 'off the cuff' statement came when asked about temperature ranges - the cleaner higher octane fuel makes a big difference when the engine is cold. The spark plug is out of it's normal working operating temperature and carbon deposits form on the electrode so causing an amount of fouling. This is burned off as soon as the range is reached... from NGK's point of view this should be the only time a benefit would be seen.

Very popular opinions state Optimax is better than Ultimate - this is possibly due to the 1 unit higher RON value. Preach all you like about fuel's but the general populous is for higher octane fuels.

The spark plug is ignored as one part which doesn't normally fail. But today's pre and post TDC spark systems (Fireblade for instance) take there toll... renew regularly with NGK Spark Plugs the OEM's choice!

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Originally posted by jambojeef
Agree with the above,

Bike engines generally run a higher compression ratio than car engines and so would have been designed to run a higher octane fuel to prevent detonation. An R1 will almost certainly be best run on 98RON.

Geoff

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My good old 1700 crossflow had a hiccup going down to South of France - I have a 20 litre tank and had to stop every 130 miles to fill up. Halfway down France it was dark and I was tired so I filled up the car as usual. The fuel seemed to last forever, I'd only used just over half a tank, and the odo. read 122 miles!! I was a bit freaked out 'cos I thought I'd get stuck in the middle of nowhere so I filled up again anyway. Seemed I'd put optimax in instead of 'super' unleaded.
I'm definitely a convert now!

Marcus

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Originally posted by jimgiblett

Higher compression yes. Will run better on 98. No, not unless the timing is advanced. If the engine was manufactured for 98 it would knock on lower grade fuels and as the R1 manual says normal pump gas in its service manual that means petrol down to around 90 would be okay. Mr Yamaha would be getting lots of warranty claims from riders who have put lower octane fuel in their bike.

If you want to take advantage of 98 octane fuel with a R1 get an ignition advancer else you are wasting your money.

ps my R1 passed SVA with Tesco 95 with very low emissions no problem.

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My gut feeling - based on no known science - is that Optimax is the only fuel that effectively replaces good old leaded 4-star in my x-flow Locost.

There is no reason why I should need a higher octane, as the compression ratio remains the same, and I used to run with the standard timing. The main difference now is that I shift more fuel through the engine (bigger carb, better filter) and let the exhaust out a bit quicker (better manifold & exhaust).

I have no experience with super unleaded, as it's hard to find round my way, neither have I tried the BP stuff - anyone know how this compares to Optimax?

rgds,
David

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Originally posted by Hellfire

Well I'm sorry Jim but you have totally contradicted yourself within three paragraphs. If Mr Yamaha made his engine to suit down to 90 Octane then running it on 95 would have no effect... conversley 98 Octane in a 95 Octane designed bike would also have no effect!

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Originally posted by jimgiblett
Contradicted... How??

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Originally posted by smart51
[ It is the difference between "beter" and "the most better it can possibly be".

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Fozzie..That fuel supplied at LeMans is a loooooong way from normal pump fuel! And a lot closer to 100 octane avgas than they would have you believe!!!

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Originally posted by jimgiblett
Deviation from this optimum by definition is negative.

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Originally posted by smart51
[No, it can sometimes just be "not any more positive"

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Originally posted by jimgiblett

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Originally posted by smart51
[No, it can sometimes just be "not any more positive"

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And that must be worth paying the extra pump price for !

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Originally posted by Syd Bridge
Fozzie..That fuel supplied at LeMans is a loooooong way from normal pump fuel! And a lot closer to 100 octane avgas than they would have you believe!!!

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A lot of the higher octane fuels have oxygenators added to clean up the combustion...

These oxygenators act like mild nitrous oxide and on the dyno we have seen a few bhp increase accross the curve, but to utilise them properly you normally need to richen the mixture very slightly..

Octane rating in itself does nothing for the fuel except let you run more advance, which is good, as almost every bike engine out there has an ignition advance kit you can buy...

Or of course you can run a PC111R which allows ignition adjustment as well as fueling...

Every bike I have owned has run better on optimax, Yamaha Fazer thou, ZX6R and Duke 748...

Same views as the rest of you on NGK plugs...

No substitute in my eyes anymore for a bike...

In my old Pug 106 Xsi the engine ran the temp needles width lower with Optimax. This made the difference between the fan being on and off.

I have a Corolla T-Sport now which has the Lotus Exige engine in it with variable valve lift. With Optimax I can feel the surge of power come in much harder. In fact if the road is anything but dry when I hit 6250RPM in 2nd gear the traction control kicks in until I change at 8200RPM!

As I understand it you will only notice gains using higher octane fuel if you run more ignition advance, principle being more advance = more power, and higher octane means you can run more advance before you start pinking (aka detonation aka knock).

Some cars, nasp as well as turbo, have a knock sensor which the ECU will read and retard the ignition if it detects knock. This should mean the ECU can run maximum advance all the time, however; the ECU may only run up to a maximum target ignition advance value (for given revs, load etc), which may not take full advantage of the fuel you put in.

More significantly the ECU may not try and re-learn its adaption values if you have driven the car for a while, then put in higher octane fuel - meaning you will see no gains. It may require an ECU reset (disconnecting the battery for several minutes may do this).

Other advantages of premium fuels such as cleaning additives (and oxidising agents? first I'd heard of them..) may also be a factor, but the octane rating alone is only of interest if you are tuning your ignition advance to suit.

I think it's also important to remember that psychology is a factor. many people are convinced by advertising that putting optimax in their car will make it livelier, and convince themself that their car is faster / more responsive / sounds better / smells sweeter running optimax. Placebo effect, if you will.

Then again, the detergents in the first tank of optimax they put through the engine probably did do it a favour, but that doesn't mean it's worth running optimax all the time..

P.S. ooh! 1000 posts! go me! (to the garage instead of waffling)
[Edited on 3/11/05 by blueshift]

[Edited on 3/11/05 by blueshift]

Fuel test in the latest EVO mag