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Canadian manual say to use unleaded gasoline with pump octane rating of 87 (R+M)/2, which is same rating in USA.
 

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Regular, premium is just throwing money away. The engine is designed to run on regular.
 

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Premium can sometimes make an engine not designed for premium run hot. I've always heard if the engine does not knock regular is fine.
 

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Regular, premium is just throwing money away. The engine is designed to run on regular.

That is right. The user friendly Burgman will happily burble along on any good drink of gas.

FYI, my buttometer nor my bike can tell the difference between 10% ethanol or the corn free stuff either. I just buy regular from whatever gas station I am near when the low fuel icon starts flashing.
 

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Regular. But I do try to get Chevron, if there's a choice.
 

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The only time I use non-ethanol gas is in the vehicles I don't ride/drive very often. Because it does stay fresh longer. I used to run non-ethanol gas all the time and got a little better mileage but not much. When the non-ethanol gas started costing $1 more than regular I quit using it in my daily vehicle. I didn't mind paying up to $.50 more but no way will I pay $1 more for two or three extra MPG. :rolleyes:
 

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Higher octane should make the engine cooler not hotter - slower burning fuel. However that slower burn means less energy which means less HP.

Ethanol fuel can leave deposits of crud in bad places. It is much more of a problem with older engines especially ones with carbs. The local Sams is ethanol free so I fuel up there most of the time but sometimes I fuel up at the corner pumps{Sams is on the other side of town from me but close to work}.
 

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I agree with the first reply to the OP in that link - if a modern engine is knocking on the recommended octane then something is wrong! Back in the day engines would build up carbon and that would force you to move to a higher octane. Today's fuel has very efficient detergents that should prevent those kinds of deposits from happening. If you do get heavy deposits then you have a problem with your ignition system or maybe oil is getting into the cylinder{s}, which would also be causing smoke out the exhaust. Either way the engine needs to be serviced not simply moving to a higher octane.
 

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Yes, and the main issue with using higher octane fuel than the engine was designed for is not just less hp or mpg (which can be significant depending on the bike concerned) but over time a carbon problem with the exhaust valves and seats, which also burn. The closed loop systems cannot always fully compensate for the slower burning higher octane fuels to the extent they should so you get much hotter, still burning gases going past the exhaust valves. Last year I replaced both exhaust valves on a 2009 400 that had been run extensively at speed on high octane. I was able to just regrind the seats and all was ok. But the owner thought it was doing the engine good and he would get better hp and fuel economy. The reverse is true.
 

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I run 87 in my 650's. I use non-eth gas when I can. It seems to like that a bit better, but really not a lot of issues. I did get a touch of ping off a bad tank of 87 winter blend on my old one a few years back. MPG was bad on that tank too, but that's really the only time i had a major issue.
 

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It seems this bears repeating:

Octane rating has nothing to do with the hotness or coolness of a fuel's combustion process, or how powerful the fuel is; nor does higher octane fuel "burn slower" than lower rated fuel.

The octane rating is ONLY a measure of a blend's ability to resist detonation, an engine being fed higher octane fuel will not run any cooler than when running a lesser grade.
 

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Whilst what you say is correct Cliffy, it's not as clear cut as that and speedandstyle makes a good point. We are talking here about putting higher octane fuel in an engine that doesn't need it and that wasn't designed for it. Under those circumstances it's proven that too high an octane fuel will burn too slowly for that engine compared to using it's "designed for fuel", and can damage the exhaust valves and seats. Under those circumstances an engine will produce less power as some of the charge is then wasted, since it's still burning as it exits the combustion chamber. You can see this effect on the dyno and in the lab engines when making any comparison with these fuels in a particular engine that's not designed to run on higher octane. On many of these engines the fuel and ignition maps won't adapt enough to make full use of the higher octane fuels so the fuel is still burning on exit from the chambers. Here is the uk there has been much publicised about this effect, especially on programs like 'Top Gear' etc where they tested differing fuels. As you will know the higher octane fuels explode/ignite in a more controlled way causing the combustion flame to spread more slowly than the violently igniting lower octane fuels (which can cause the knock we all despise). It also requires more energy to ignite higher octane fuel and it won't be detonated by high combustion temperature prematurely, thus avoiding the dreaded knock or pinging which can be so damaging to modern engines. But it requires the engine to adapt too to get the best out of it. On the majority of engines not designed for higher octane fuels we don't build in much adaption/allowance for running on anything more than the octane rating the engine was designed for. There is little point. Therefore the higher octane fuels are not only a waste but potentially, depending on the engine, harmful if used long term. Whilst you can still put in a higher octane you won't get the best out of it and if you continue to run on higher octane, the engine over time may be damaged, and at the very least will suffer from exhaust valve and seat carboning. This is a known phenomenon that occurs to our Burgmans, especially the 400's.

Regarding the running hot or cold issue, this too can be a problem of using the wrong octane fuels. Sometimes this may be evident on the engine temp gauge but usually not. Using a too low an octane fuel is normally a cause in a higher performing engine, of cylinder, head and valves overheating. You will often find the combustion chambers become too hot and this will cause the engine to 'overrun' or suffer from pre-ignition after switching off the ignition. The engine just wont stop on demand with the engine dieseling all on it's own with the engine switched off! This is on mostly carb engines where fuel flow is not cut in the same way or as definitively as injected motors. However, the top half of the engines even on injected motors will run hotter and is measurable. Also of course, the dreaded pinging can take place due to increased combustion temperatures just before ignition. Higher octane will stop all that from happening and allow the motor to run cooler (at it's designed temperature) internally.

So although the fuels themselves don't burn hotter, the ensuing problems of using a fuel that is too low in octane rating will cause the motor internals to heat up more than usual because of combustion irregularities.
 

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Quantum that was a really good explanation of what's happening in a combustion chamber. Thank you very much!

Greg
 

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I still contend that the 650's engine at 11.2:1 is a high-compression engine. There's nothing special about it (i.e. no direct injection and no ping sensor) so it must be de-tuned in the ECU maps (richer mixture? retarded spark advance?) to allow it to run on 87RON fuel. Wouldn't it be nice to re-map it to run as a 11.2:1 compression engine should, and require 91RON? Theoretically we'd see more power and better fuel economy (longer cruising range). Opinions?
 

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Mike, your bike has a closed loop system that will in effect detect any pinging. You don't necessarily need knock sensors unless the engine is a high performance unit, which the 650 Burgman isn't. When an engine pings it doesn't burn right and the engine will know what to do. Exhaust gas temps change. But that situation will only occur if you put the wrong grade fuel in. That would have to be too low an octane rating. My Burgman 400z abs has 11.2 to 1 also. It never pings on regular. These days, it isn't necessarily the compression ratio that dictates what fuel the engine can use. An example would be a GDI petrol engine with 14.5 to 1 compression ratio. It has a smart ecu that prevents damage all linked to a host of sensors around the engine. You can use regular in most of them.
 

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Whilst what you say is correct Cliffy, it's not as clear cut as that and speedandstyle makes a good point. We are talking here about putting higher octane fuel in an engine that doesn't need it and that wasn't designed for it. Under those circumstances it's proven that too high an octane fuel will burn too slowly for that engine compared to using it's "designed for fuel", and can damage the exhaust valves and seats. Under those circumstances an engine will produce less power as some of the charge is then wasted, since it's still burning as it exits the combustion chamber. You can see this effect on the dyno and in the lab engines when making any comparison with these fuels in a particular engine that's not designed to run on higher octane. On many of these engines the fuel and ignition maps won't adapt enough to make full use of the higher octane fuels so the fuel is still burning on exit from the chambers. Here is the uk there has been much publicised about this effect, especially on programs like 'Top Gear' etc where they tested differing fuels. As you will know the higher octane fuels explode/ignite in a more controlled way causing the combustion flame to spread more slowly than the violently igniting lower octane fuels (which can cause the knock we all despise). It also requires more energy to ignite higher octane fuel and it won't be detonated by high combustion temperature prematurely, thus avoiding the dreaded knock or pinging which can be so damaging to modern engines. But it requires the engine to adapt too to get the best out of it. On the majority of engines not designed for higher octane fuels we don't build in much adaption/allowance for running on anything more than the octane rating the engine was designed for. There is little point. Therefore the higher octane fuels are not only a waste but potentially, depending on the engine, harmful if used long term. Whilst you can still put in a higher octane you won't get the best out of it and if you continue to run on higher octane, the engine over time may be damaged, and at the very least will suffer from exhaust valve and seat carboning. This is a known phenomenon that occurs to our Burgmans, especially the 400's.

Regarding the running hot or cold issue, this too can be a problem of using the wrong octane fuels. Sometimes this may be evident on the engine temp gauge but usually not. Using a too low an octane fuel is normally a cause in a higher performing engine, of cylinder, head and valves overheating. You will often find the combustion chambers become too hot and this will cause the engine to 'overrun' or suffer from pre-ignition after switching off the ignition. The engine just wont stop on demand with the engine dieseling all on it's own with the engine switched off! This is on mostly carb engines where fuel flow is not cut in the same way or as definitively as injected motors. However, the top half of the engines even on injected motors will run hotter and is measurable. Also of course, the dreaded pinging can take place due to increased combustion temperatures just before ignition. Higher octane will stop all that from happening and allow the motor to run cooler (at it's designed temperature) internally.

So although the fuels themselves don't burn hotter, the ensuing problems of using a fuel that is too low in octane rating will cause the motor internals to heat up more than usual because of combustion irregularities.

Quantum, I of course agree that higher octane will cooler than lower grades--in an engine being abused by running too low octane a fuel.

it will not run any cooler in an engine that is operating properly on a lesser grade, nor will it cause any loss of power. To the contrary, most always simple re-tuning the ignition timing; to make use of the higher octane fuel's increased resistance to detonation; will increase the engine's output.

Here are changes I made recently to ignition timing for a 1998 Lincoln Mk VIII, to make best use of 93 octane fuel. Shown below is the Spark Borderline table, defining the maximum allowed spark advance for a given load and rpm. The green highlighted rows show the "bumped" timing at higher load/rpm, the row just below those rows shows the stock values:



You can see the maximum allowed advance has been increased by 2° (there is some room left for additional tweaking). There is also a scalar value in the tune, Global Spark Adder, that is always added the the calculated then table limited, ignition timing--I set that to +1.2°.

These changes and tweaking of the Stabilised Open Loop Fuel table to lean out the mix at higher load and RPMs (because Ford tuned the EECV V8s to run too rich at that end, as rich as 11.0:1) resulted in an increase of 8 to 10 rwHP (3 "back-to-back" dyno runs)--with no other significant changes to the tune or engine.

For the final word in fuels and the combustion process read Chapter 9, Combustion in Spark Ignition Engines, in John B. Heywood's Fundamentals of Internal Engines and/or Chapter 1, Combustion in Spark Ignition Engines I: Normal Combustion, in Charles Fayette Taylor's Internal Combustion Engine in Theory and Practice.

I had the privilege of studying under Dr. Heywood at MIT in the late 60s/early 70s, and have met Dr. Taylor, both are gentlemen one would not want to argue with over ICE theory and operation.
 
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