Best petrol for my bike?

[sil3nt]

http://faq.ninja250.org/wiki/What_ki...hould_I_use%3F

And im 90% sure that their87 is our 91

[Old Steve]

There are actually two types of octane - RON (Research Octane Number) and MON (Motor Octane Number. One measures the petrol's resistance to knock at high revs, one at low revs like pulling away, and I can't remember but I think RON is the high rev octane. 91 and 95 refers to the RON of the product. There is no MOE spec for 98 - that is just petrol which comes out of the refinery with a higher RON because the refinery couldn't meet the RON number without having to "give away" a higher RON. For 91 RON petrol, the MON spec is from memory 81 min, for 95 it is 85 I think.

There is extremely little or no gain in using 95RON petrol in an engine designed for 91 RON petrol. Consult your manufatcurers handbook and use what they recommend. You may like to avoid those higher octane petrols which contain ethanol, some elastomers don't like the stuff.

So read the book and use the petrol which the bike maker recommends.

In America they use an octane system which is the the average of the RON and MON, so their 85 octane petrol is equivalent to our 91 RON/81MON, their 91 is our 95RON/85MON. So an American bike manufacturer recommending 91 octane gasoline wants a petrol with an average of RON and MON of 91, i.e. our 95 RON "super". If they ask for an 85 octane gasoline, thats our 91 RON regular.

Japanese and European bike manufacturers would recommend the fuel by its RON number, Japanese and European petrols are usually 91RON/81MON and 95 RON/85MON, or very close to that. The NZ unleaded petrol specs were largely based on European standards at the time - the early 90s.

[Slyer]

I just chuck Shell 95 in there. Same as my car.
I get measurably better mileage out of 95 with my car, not sure about the bike.

[R-Soul]

My bike knocks when I use 91 or even 95- and settles nicely when I use 98.

Octane number indicates the fuels propensity to "pre-ignite" in the cylinder (and should not affect carb/injected bikes differently).
91 will pre-ignite more readily than 98. AVGAS has the least danger of preignition.

Pre-ignition happens when a combination of engine temperatures and pressures cause the fuel to ignite (effectively explode) when it is not supposed to. This exploding (as opposed to burning) timing is out of synch in the engine, and can act to counter the momentum of the piston, and makes the bike "hiccup" (almost stop mid-idle, and then start again when the next cylinder fires at the right time- sometimes it can make an engine stall if it is idling low). Also, the simultaneous explosion of all teh fuel is not as efficient or effective at generating pressure in the cylinder as a proper "burn" from the center outward.


Preignition happens when you have engines with high compression rations (higher compression leads to higher temperature buildup and the onset of preignition, since compressing gas makes it hot (remember how pumping your bicycle tyres heated the pump up?).
It also can happen when a bike is running hot or when it is running on very advanced timing (such as racing engines - which is why they use avgas).

But generally you just need to follow the manufacturers recommendations.
Octane value does not add more "power" or volatility to the fuel or anything like that. So if your engine is designed for 91, then 98 will not add anything else to your bike's performance.

[revlikeshit]

Use the best fuel available to you.
Anyone who actually knows anything about engines will tell you that. 91 is shit, in all my bikes ive always run atleast bp 98( 2strokes and 4strokes -ss600's 250's etc).
As has been said bikes tend to run alot higher compression than most cars and hence should be run on higher octane fuel.Check what the manufactuere says though.
Even a gpx has high comp. (compared to a car) use 95/96 or above..

Yeah it may 'be sweet as' and you might not notice much difference, but it is a proven fact.
Theres a reason you dont run a race bike on 91...

Like the guy i saw putting 91 in his 04 zx 6'RR' Race Hom model ( 599cc - 13.9 .1 compression stock) ... um thats gona do your top end some good aye..haha

[YellowDog]

I had a similar problem with my wife's car. 95 seemed to make a big difference and stopped the knocking. I also got 100km per tank more out of it.

After having major service plus new HT leads, I'm back to 91 on it and also still get the 100km extra out of a tank.

If your bike has an Electronic Management System that can auto adjust the timing for differing fuel grades, then you can stick higher octane fuels in without a problem.

I use 95 in my bike.

[CookMySock]

91 works fine.

Yes 91 is all good. On some bikes you get a better range from the same litres, using higher octane fuel.

Steve

[R-Soul]

Yes 91 is all good. On some bikes you get a better range from the same litres, using higher octane fuel.

Steve

That actually contradicts itself.
If 91 works well for an engine designed for it, then it will not cause knocking (because of low compression ratios, and no advanced timing etc) . If it causes knocking, then the engine preformance will be affected by the piston being pushed in the wrong directions at the wrong times during the combustion cycle, and will be more inefficient.

But because knocking is also an uncontrolled explosion instead of a burn, it is bad for your pistons and cylinders, and can cause metal erosion and other damage in your engine. The fact that you get better fuel consumption when using higher octane means that 91 IS causing knocking (even if its not obvious to you from hearing it), and therefore you should avoid it if it makes such a drastic efficiency difference, or make sure your engine is tuned properly.

PS I am talking about when the engine is tuned properly - as the state of tuning can affect whether it knocks or not (the ignition timing is obviously affected by tuning).

[steve_t]

Higher octane fuels also have a slightly higher calorific value per litre, ie more energy per litre, so you will get slightly better range from a tank. But you're right in that if the increase in range is significant, it's because the engine can advance timing enough to get a more efficient burn

[R-Soul]

Higher octane fuels also have a slightly higher calorific value per litre, ie more energy per litre, so you will get slightly better range from a tank. But you're right in that if the increase in range is significant, it's because the engine can advance timing enough to get a more efficient burn

That is if teh engine is advanced enough to change its own timing. But many are just set mechanically and then if the incorrect fuel is used, it just knocks pieces off the pistons (if you'll excuse the pun).

This is a good explanation.
http://en.wikipedia.org/wiki/Octane_rating

[marine0089]

The manual states you should use 91.

Any service station's 91 is fine ...Especially if you run out of gas and are pushing the little bugger.

[scracha]

Theres a reason you dont run a race bike on 91...

Like the guy i saw putting 91 in his 04 zx 6'RR' Race Hom model ( 599cc - 13.9 .1 compression stock) ... um thats gona do your top end some good aye..haha

Fuck.......so that's why she blew

[kwaka_crasher]

I ran 98 in my Hornet for two years before being told by a well known and very reputable mechanic that 98 was no good for my bike being carburettored.

Whether it's carburettor or injection makes no difference.

+1 to that too...I actually found that the 96 (thats what I had in it) created a flat spot in my cbr around 10-14k RPM, disappeared when I went back to 91

That's more about ignition timing curve for that fuel than the fact it's carburettored.

It's all the same. Apart from that Gull ethanol blend, it all comes from the same refinery.

The different companies add different additives prior to delivery.

I had a similar problem with my wife's car. 95 seemed to make a big difference and stopped the knocking. I also got 100km per tank more out of it.

After having major service plus new HT leads, I'm back to 91 on it and also still get the 100km extra out of a tank.

Have you tried it back on 95 after the tune... if the ignition timing is adjustable (depends on the car) you can advance the ignition timing and get even better economy.

If your bike has an Electronic Management System that can auto adjust the timing for differing fuel grades, then you can stick higher octane fuels in without a problem.

I know of no production bike that can do this. I also know of no production bike that even has a knock sensor to retard the timing in the event of detenation, although there may be some in very recent years. But they've only added O2 sensors in the last couple of years for closed loop fuel injection - until then it was open loop meaning there was no feedback to the ECU to control injector pulse width based on air/fuel ratio at any given rpm so if it was wrong it stayed wrong until manually adjusted and even then the manual adjustment only sets the baseline so if it's rich at low rpm and lean at high and it's adjusted to be more rich it'll be richer across the entire rpm range.

That is if the engine is advanced enough to change its own timing. But many are just set mechanically and then if the incorrect fuel is used, it just knocks pieces off the pistons (if you'll excuse the pun).

While the timing base is set mechanically using an inductive crank angle sensor, the timing itself is changed solely by rpm in most cases (sometimes by load via a MAP sensor or TPS). But like I said before, I'm unaware of any production motorcycle that adjusts it's ignition timing based solely on fuel.

[Tryhard]

So now I'm realy confused.
When I was driving around in VW's I used to set the timing to the petrol I wanted to use taking in account the plugs I was also running.

However in std form I guess 91 is the right choice. I will run it for a couple of thou and check the plugs I guess.

Thanx for all the replies

[sosman]

91 for the road &..... 98 for the trackday's