Octane rating - which fuel for bikes?

[oldnslo]

I've learned when to give up, Ron. It's opinion over science, always, and that is definitely a sweeping generalization.

[ronboskz650sr]

I've learned when to give up, Ron. It's opinion over science, always, and that is definitely a sweeping generalization.

May I join you now?

[High_Side]

Bikes are not cars...John, can you hear my head hitting this wall?

Wow. I'm not sure how we arrived here so quickly in this thread...... Did I miss something?

[TechTMW]

Taken From http://www.cs.uu.nl/wais/html/na-dir/au ... part3.html

6.13 Can higher octane fuels give me more power?

On modern engines with sophisticated engine management systems, the engine
can operate efficiently on fuels of a wider range of octane rating, but there
remains an optimum octane for the engine under specific driving conditions.
Older cars without such systems are more restricted in their choice of fuel,
as the engine can not automatically adjust to accommodate lower octane fuel.
Because knock is so destructive, owners of older cars must use fuel that will
not knock under the most demanding conditions they encounter, and must
continue to use that fuel, even if they only occasionally require the octane.

If you are already using the proper octane fuel, you will not obtain more
power from higher octane fuels. The engine will be already operating at
optimum settings, and a higher octane should have no effect on the management
system. Your driveability and fuel economy will remain the same. The higher
octane fuel costs more, so you are just throwing money away. If you are
already using a fuel with an octane rating slightly below the optimum, then
using a higher octane fuel will cause the engine management system to move to
the optimum settings, possibly resulting in both increased power and improved
fuel economy. You may be able to change octanes between seasons ( reduce
octane in winter ) to obtain the most cost-effective fuel without loss of
driveability.

Once you have identified the fuel that keeps the engine at optimum settings,
there is no advantage in moving to an even higher octane fuel. The
manufacturer's recommendation is conservative, so you may be able to
carefully reduce the fuel octane. The penalty for getting it badly wrong,
and not realising that you have, could be expensive engine damage.

Motorcycles don't have sophisticated fuel management systems. Even the most advanced Fuel Injection system on a bike does not have an anti-knock sensor. So, just as this essay says, it's up to us to determine the best fuel for our bikes. Most of us don't like to throw away money, so it makes sens to run the lowest octane fuel possible for our bikes. Some of us have more experience than others when it comes to detecting knock or preignition - so the "try what's best method" may not be for everyone, in which case it's simply best to stick to your manufacturers recommendations.

[oldnslo]

What many of the posters have advocated is, rather than use the fuel indicated as required by the manufacturer for a given bike, go directly to premium and angels will dance on your shoulders and bluebirds will tie your shoe laces, and every day is summer, and all vehicles will perform in a superior manner. Some of us say some bikes, and other vehicles, are designed/tuned to run well on lower octane fuel, and we are merely pointing out the lack of advantage in using a higher octane, more expensive fuel. Why buy a dump truck when a wheelbarrow will do? That's all.

[ZooTech]

What many of the posters have advocated is, rather than use the fuel indicated as required by the manufacturer for a given bike, go directly to premium and angels will dance on your shoulders and bluebirds will tie your shoe laces, and every day is summer, and all vehicles will perform in a superior manner. Some of us say some bikes, and other vehicles, are designed/tuned to run well on lower octane fuel, and we are merely pointing out the lack of advantage in using a higher octane, more expensive fuel. Why buy a dump truck when a wheelbarrow will do? That's all.

He has a point, assuming anyone is saying premium gas will make every engine run better. Octane is a chain of eight carbon atoms...a polymer...and the more octane present in a given fuel, the slower and cooler it burns. If an engine is designed to run on quicker-burning 87-octane, that is what will work best. Without the ability to advance and mentally challenged the spark in response to predetonation, motorcycle engines rely on their owners to use the proper fuel. Knock is not always something you can hear with the naked ear, either...so don't rely on that alone to determine if your bike is running fine on lesser fuels. Just stick with the manual, and make the proper adjustments at altitude. Why anyone would risk damaging a $3000-$20000 motorcycle just to save a few cents at the pump is beyond me...unless the manual says 87-octane is good to go.

[MarkyPancake]

95 RON Unleaded petrol is most common in the UK and bikes and cars of recent years are built to run on at least this, but I have found my R1 runs better on Super Unleaded which is 97+ RON and is usually a few pence more expensive. We have Shell Optimax which is 98 RON and some supermarkets are trialing 99 RON (both are super unleaded fuel).

[BudmanTom]

My bike has 10.5-1 compression but it only calls for 87 octane.




Tom

[ZooTech]

My bike has 10.5-1 compression but it only calls for 87 octane.

Contrary to popular belief, compression ratio is not necessarily an indication of which octane fuel is needed. There are many other factors to consider.

[Buelligan]

My Owners Manual says to use a good quality gasoline, Octane rating of at least 91 (95 RON).

But aside from that, you do get better mileage with the higher Octane, so there probably isn't any cheaper to use the low Octane.