91 vs 95 octane?

[Adriaan]

Does anyone have a preference and why ? Are there any pro's or con's to either ?

:D Thanks

[Latte]

Use the lowest octane you're bike is rated for. All my bikes are 95 (but they run fine on 98). My cars are all 91.

The lower the octane the more chance of detonation. But the faster flame front should produce more power if it's tuned for it.

[flyingcr250]

I heard european/american RON95 was the same as our 98

[Jay GTI]

We measure RON, whereas the Americans measure PON, which is an average of RON and MON (RON being the higher value).

[Sable]

Also DON and JON, don't forget

[thecharmed01]

Depends on the vehicle.
When it comes to cars, I'll always run the highest octane I can get as Japanese imports (which is what I drive most often) are all tuned and built to run on higher octane fuel than anyone supplies here.
If you do have a japper, then you are better to run as close to 98 as you can get.

I'm not sure if the same applies to NZ built cars though as I would hope they are tuned for NZ fuel, which is not overly good.

I don't think there are any fuel companies providing a true 98 octane fuel here. They might call it 98 but it isn't. BP have the closest with their high octane fuel, which is not at all stations and we try to only use the BP high octane in the bikes.
I would never run 91 in my bike if I didn't absolutely have to as higher octane fuel delivers more power. And it's all about the power isn't it :banana:

[wickle]

[QUOTE=Latte;1130212328]Use the lowest octane you're bike is rated for. All my bikes are 95 (but they run fine on 98). Cars are all 91.

incorrect : some euorpean vechilles are 95 or better

[Fast Eddie]

Use the lowest octane you're bike is rated for. All my bikes are 95 (but they run fine on 98). Cars are all 91.

The lower the octane the more chance of detonation. But the faster flame front should produce more power if it's tuned for it.

Cars are not all 91..

[barty5]

just use 95 or 98 forget about using 91

[Jay GTI]

also don and jon, don't forget

don jon son?

252383

[onearmedbandit]

91 is crap. Wouldn't even run it in my lawn mower.

[bsasuper]

Ron makes the fuel sound good, take 3 points off to get the right figure

[Latte]

[QUOTE=Latte;1130212328]Use the lowest octane you're bike is rated for. All my bikes are 95 (but they run fine on 98). Cars are all 91.

incorrect : some euorpean vechilles are 95 or better

Sorry, meant My cars.

[Jay GTI]

Depends on the vehicle.
When it comes to cars, I'll always run the highest octane I can get as Japanese imports (which is what I drive most often) are all tuned and built to run on higher octane fuel than anyone supplies here.
If you do have a japper, then you are better to run as close to 98 as you can get.

I'm not sure if the same applies to NZ built cars though as I would hope they are tuned for NZ fuel, which is not overly good.



Common myth, they have the same octane fuels we do, the only difference is they can get 100RON as well. But the idea they are all running around with tanks of 100+RON super fuel isn't true.




I don't think there are any fuel companies providing a true 98 octane fuel here. They might call it 98 but it isn't. BP have the closest with their high octane fuel, which is not at all stations and we try to only use the BP high octane in the bikes.

From what I understand no-one gets a true 98RON fuel, worldwide it's made by taking a lower RON fuel and mixing it with octane-boosting additives. Some people believe these additives leach out within 2 weeks of production, so that by the time you put it in your car it's not 98RON anyway.




I would never run 91 in my bike if I didn't absolutely have to as higher octane fuel delivers more power. And it's all about the power isn't it :banana:



Another myth sorry, higher octane doesn't equal more power. The octane rating is simply a method of measuring the resistance to detonation. From that, the higher the octane, the higher the compression ratio you can use, or the further the ignition advance you can set. On something relatively dumb, like your average carb-fed dirt bike, using high octane fuels will gain you absolutely no power at all over a low octane fuel, unless you map or change your ignition to suit (it's generally static). However on most modern cars the ECU is intelligent enough to be able to actively monitor detonation and advance or retard the ignition to suit the RON of the fuel you're using, so theoretically you'd make more power on 98RON fuel over 95RON or what ever. But even then, in terms of actual, real-world power increases, it's so minimal you won't notice.

[Pornstar]

Why the duece do we get all these road bikers givin there 2 cents on this page?

[Fast Eddie]

Why the duece do we get all these road bikers givin there 2 cents on this page?

haha.. cause an internal combustion engine is an internal combustion engine.. doesn't matter if its a 450cc single banger in a dirt frame or a 4 pot in a road frame

[Mort]

You should use the fuel rating your engine is designed for...using a higher octane wont make a bit of difference. If the engine is designed for 91, it will make no difference using 95 because the engine will not produce the compression that may cause detonation that 95 octane will prevent. (did I say that right ?) 95 is meant for higher compression engines.

There is one exception I agree with... if you are running at a trackday say, you really dont want detonation happening at high engine revs and if you got a dodgy batch of fuel (it happens) then you best mitigate that situation by using 95.... but you wont get anymore power from it.

[morg_nz]

98 - from gull only. there is way too much variability in nz octane ratings - i'e heard of some "91"s being as low as 85 - 87 in tests. at least if you run 98 you have a chance of getting a semi decent octane. and as bp and gull are the only ones with 98, and bp charges like 5c more per litre, go to gull. Also, its not like its race fuel - 98 aint going to blow anything up, it just burns way cleaner and better combustion = more power. simple.

[caspernz]

91 is fine for the lawnmower....

Car and bike can run on 91, but I find that I get more kms per tank if I run on 95 or 98 (where available). Over the years, tested it various different ways and for me the highest grade of fuel gives the lowest running cost, ie cents/km. The bike feels more lively on 98, good enough for me to use it where I can.

[CRF119]

All i can say is use the same fuel each time that way you know what your bike should perform like when you get to a ride. I always use BP 98 in every thing, ill go out of my way to get it. A friend of mine stopped by Mobil and brought 98 because he had no time to stop by BP, his bike wouldn't even run on it! We drained the carb and the tank put my BP 98 in and it started right up. I am sure my Van gets more Kms on 98, it can't retard the timing enough to run properly on 91.

[NordieBoy]

My VT250 and Nordwest preferred 95 but the XR250, DR650 and TT350 prefer 91 for a noticeable bottom end improvement.

The VT and Nordie were much higher compression than the others.

[JMemonic]

Just a little note, the octane rating is not, does not, and never will relate to the power a particular fuel will generate, it is a measure of how it burns in a controlled environment. 98 RON will deliver no more power in a vehicle designed and tuned for 91 than 91 will, if you want to spend the money dyno your vehicle same day same conditions just change the fuel and see if you get a increase in output.

RON in a measurement determined to a scientific scale, 91 RON in NZ is 91 RON in the US blah blah.

Further reading (http://en.wikipedia.org/wiki/Research_Octane_Number#Measurement_methods)

Oh as a side note F1 cars are limited to pump gas at 91 octane, this is tested by the governing body.

[scott411]

in any late model 4 stroke mx bike i would run minimum 95 octane,

[p.dath]

Does anyone have a preference and why ? Are there any pro's or con's to either ?

:D Thanks

I'm price sensitive, so I use 91.

[Jay GTI]

RON in a measurement determined to a scientific scale, 91 RON in NZ is 91 RON in the US blah blah.



Except that if you go to the US, you will see an octane number on the pump, as you do here and it will not be the same as you see here, because they list the PON, not the RON as we do. But if you'd read any of the previous posts... ;)

[JMemonic]

Except that if you go to the US, you will see an octane number on the pump, as you do here and it will not be the same as you see here, because they list the PON, not the RON as we do. But if you'd read any of the previous posts... ;)

I did, if you re-read my post I was not talking about what they display on the pumps, I stated that RON or research octane number is gained by a scientific test and thus will be the same no matter the country:msn-wink:

[willytheekid]

Got PhatGirl tuned up to run on the cheap petrol :bleh:...mind you....Being a two valve guzzi, she would probably run on potatoe juice :wacko:

Cost was my driving factor...not performance (As long as no damage to the engine occurs)

[Jay GTI]

I did, if you re-read my post I was not talking about what they display on the pumps, I stated that RON or research octane number is gained by a scientific test and thus will be the same no matter the country:msn-wink:

Which, by and large, had already been covered. :bleh:

[ICE180]

much better quailty 98 has had a much better refinery process
91 will go off quicker if left in a tank compared to 98 has happen to me

[onearmedbandit]

I'm price sensitive, so I use 91.

Ever worked out how far a tank of 91 gets you compared to 95? You may find you get more km's per tank from 95 (note may) therefore giving you better bang for your buck.

[F5 Dave]

much better quailty 98 has had a much better refinery process
91 will go off quicker if left in a tank compared to 98 has happen to me
What? The base stock will be the same. They alter the fuel by adding more arromatics to it to increase the octane.


All i can say is use the same fuel each time that way you know what your bike should perform like when you get to a ride. I always use BP 98 in every thing, ill go out of my way to get it. A friend of mine stopped by Mobil and brought 98 because he had no time to stop by BP, his bike wouldn't even run on it! We drained the carb and the tank put my BP 98 in and it started right up. I am sure my Van gets more Kms on 98, it can't retard the timing enough to run properly on 91.

I love anecdotal stories. Its the same gas. BP & Mobil do swapsies when one of them is running low.


By the way if there is still some doubt on Octane etc- do some google research & look up calorific value. This is the energy of a fuel. It is not octane related. Its like saying your can of coke has more caffeine when its bubbly. Rest has been covered above.

But look up methanol. Low calorific value, but sky high octane. Pour heaps in (because you need more to make power) & crank the compression up silly high & you can make more power. Don't bother even trying it though.

[Jay GTI]

But look up methanol. Low calorific value, but sky high octane. Pour heaps in (because you need more to make power) & crank the compression up silly high & you can make more power. Don't bother even trying it though.


I can't remember the details, but recollect a story about one of the bigger names in MX trying methanol in his factory 2T 250 a decade or so ago. From what little I can remember, it made the power delivery so angry it was barely rideable and he was getting considerably higher lap times.

[F5 Dave]

rules haven't allowed it for some time except in classic roadracing, not even sure if its still there, but you have plenty of time on a big road track compared to dirt.

[Reckless]

I can't remember the details, but recollect a story about one of the bigger names in MX trying methanol in his factory 2T 250 a decade or so ago. From what little I can remember, it made the power delivery so angry it was barely rideable and he was getting considerably higher lap times.

In a 2smoker?
I ran Methanol in my race kart for about 7 years which had various MX based 125 engines. The benefit of methanol is the fact that it runs so much cooler, not that it produces power as a different fuel instantaneously. You use methanol so you can up your compression and timing to gain power not because you use methanol as a fuel par-say. You also use a shit load more of it so in a smoker its a lot harder to get them to run clean down low because you need it to deliver so much more fuel flat out! We had looong sharp tapered needles, We also run manually adjustable power jets feed directly from the fuel bowl that dumped fuel into the inlet which we could adjust on track while racing that meant we could move the main jet tuning more towards the mid range (esp when road racing).

In an inline four stroke?
Mind you in saying that we just gained 20 or more horsepower on the 1982 GPZ1100 goin from petrol (avgas) to meth and not doing a thing to the motor. Bearing in mind this is a race engine already with cams, higher compressions and Non std ignition. Tuned on the dyno of coarse :) The GPZ did about a litre per lap on Sat at Hampton Downs.

But in saying the above and getting back on topic!
In a crf450r you might find a difference between 91 and 98 because its a already fairly high performance 4 stroke engine??
Try it? It may start a little better when hot and it may feel a bit different! But if your on the way to a meeting and cant find a 98 pump you aint gonna stuff you engine on 91 octane. In my Ktm 200exc, the SV1000 and in the car I use 91 and wouldn't notice the difference if I used avgas or 98 in all those modes of transport without some engine or ignition mods on a dyno.

[F5 Dave]

on my GG 200 enduro I raised the comp somewhat (after optomising the squish it went too high & had to reduce the com to get a suitable ratio), but it was still heaps higher than std (can't remember the figures of hand). I was running 1/2Av & 1/2 91. Lead is wonderful stuff & you get big gains in Octane with just a little but have to add exponentially more to get further gains. Of the available aromatics it is the buss, at least for sensible coin.

Pure Av is supposed to hurt throttle response. All aromatics do I think. Never noticed it in Bucket engines, but ran the dirtbikes 1/2 1/2 just in case & never bothered to experiment running pure.

[caspernz]

All i can say is use the same fuel each time that way you know what your bike should perform like when you get to a ride. I always use BP 98 in every thing, ill go out of my way to get it. A friend of mine stopped by Mobil and brought 98 because he had no time to stop by BP, his bike wouldn't even run on it! We drained the carb and the tank put my BP 98 in and it started right up. I am sure my Van gets more Kms on 98, it can't retard the timing enough to run properly on 91.

Mmmmm, the one about BP and Mobil 98 being that different still has me laughing.....at times it comes from the same tap. How do I know? Aaahh, in the industry.

The Gull thing with ethanol added is a tricky one, for the calorific value of any fuel with ethanol added is lower, thus you need more fuel to make the same energy. In plain english, a tank with an ethanol blend won't get you as far as a tank without ethanol. Try it for yourself, it's quite easy to see the difference.

The basic thing is, if your vehicle can run on 91 you won't get a performance improvement running on 95 or 98, just more miles from the tankful.

[scott411]

the last time I remember methonal being used in NZ motocross was around 1991, when both Darryl Atkins and Shayne King ran 125's on it, i think it was banned from most MNZ sport after that, (i think the exceptions are bears racing and classics)

It was always tricky to use, but i am sure Robert Taylor would know a heap more about it than I would, I think they got a heap more gains back a while ago from air cooled motors where the lower burn temp had a good effect,

as said above, in my 125's i ran 50/50 avgas and 91, lead is wonderfull in two strokes for keeping denotation away,

[F5 Dave]

back in the day (haha, it doesn't seem that long ago cause it wasn't) in my race 50 with silly high compression ratio (got up to 19:1 full stroke) it loved the old 96 Super leaded pump gas ()it was Red remember?. The first batch of piss unleaded came & it barely pulled on the dyno & from that point on we changed to Av gas & the rules changed to allow it. Try as I might with jet changes, every conceivable ignition timing change & 3 different head shapes & altering the com; I still made 5% less power on Av Gas from 96 Super leaded. Pity they got rid of it in some deluded greenie initiative.

[Jay GTI]

the last time I remember methonal being used in NZ motocross was around 1991, when both Darryl Atkins and Shayne King ran 125's on it, i think it was banned from most MNZ sport after that, (i think the exceptions are bears racing and classics)




Yeah dredging the furthest recesses of my addled brain, I'm pretty sure the story I read was something along the lines of it was end of season, one of the mechanics was from a snow mobile tuning background (methanol is still used in drag racing those things as far as I know), so they had a play with this guy's 2 stroke race bike. Tried finding the story last night, but no luck...