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It doesn't matter. Most people use 87 and have no problems. It's the old fallacious pot leads to heroin argument.
87 octane won't cause a problem, but too high an octane can cause a problem with valves. If the fuel burns too slow and builds up carbon the valves can start to leak. Burning oil can cause a similar issue. Especially on higher mileage vehicles 50,000+ miles. The OP's post seems like the problem came on too quick for either of these to be the case.
 

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Discussion Starter · #3 ·
I used to think high octane burned slower. Further investigation indicates that's not the case. It's harder to ignite spontaneously but not necessarily slower burning. I like the following info. RK Tek 2-Stroke Heads: Exposing the Myths of High Octane
I read that article and as far as I can see, it explains it the way that I have understood it since I was a Construction Mechanic in the SeaBees. The arguments about complete burn and explaining that a high RPM Pro Stock engine needs to burn quickly are misleading. Of course a Pro Stock needs the fuel to burn quickly and the conditions of its combustion is quite different then a stock motorcycle. Put 87 octane in that Pro Stock and it will ignite quicker, and burn quicker then the fuel used in their example. Thus the 118 octane fuel will ignite slower and burn slower then the 87 octane fuel. I guarantee it.

Octane is the only number we really have to go by. What I was taught was that you should use the lowest octane fuel that you can without inducing detonation. Using a higher octane may cause your combustion chamber and valves to get carbon buildup. It really depends on those other factors as described in your linked article. Different brands of fuel may be quite different in their burn rate after ignition.

I know of people that have used higher octane ratings without any problems and I now of people that have had to have the heads removed and valves redone because of it. I even have one friend that twice had to have their Jetta's head removed. They then believed me about the fuel they were using and didn't have a problem after that.

I personally don't know of anyone that has had a carbon buildup problem using the correct octane.
 

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I used to think high octane burned slower. Further investigation indicates that's not the case. It's harder to ignite spontaneously but not necessarily slower burning. [/url]
TOO MANY people fall for the marketing hyperbole, where the label: "Premium" is used to designate a higher "Octane". These people reflexively think "Premium" is MUCH BETTER than "Regular", or "Mid-Grade".

Unless you have a high-compression engine (or intake pressures are boosted by a Turbo- or Super-Charger), or, have a malfunction from too much carbon build-up, you are simply spending more for fuel than you need to spend if you choose something other than "Regular Octane" fuel.

The different grades have NOTHING to do with Quality. The different grades are not technically even about the percentage of Octane molecules in modern day fuels. The different grades are actually about averaging the Research Octane and Motor Octane calculations.

There are low-quality "Premium Octane" fuels, and very high quality "Regular Octane" fuels. In fact, some of the materials use to boost RON/MON can cause problems. The point is: use the lowest rated Octane fuel your vehicle is designed to run on, and, if you wish, add your own little bit of extra cleaner (Techron or Fuel Power, to name two) to ensure you have a good quality fuel.
 

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Since different brands come from the same refineries, I would go on to say the differences in the same octane ratings of different brands is in the additive packages. The only advantage I can see in higher octane fuels is if the additive package is better. I like to use the lowest octane fuel available that doesn't cause pinging but has a good additive package to keep things clean. Since six top auto makers established a standard for additive packages in all grades seen at Top Tier Gasoline , I like to stick to those brands. Since I've never had any of my vehicles ping, I use the lowest octane available in those brands including 85 in higher elevations. I have never had an engine problem or a bad fuel problem.
 

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Discussion Starter · #6 ·
Since six top auto makers established a standard for additive packages in all grades seen at Top Tier Gasoline
I hadn't seen this before. I'll have to make sure the places I get gas are on this list.

My 81 GS1100E is the only bike that I have had that was fussy about octane and brands. My user manual for it recommends trying different brands of fuel when experiencing pinging using 89 octane.
 

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I hadn't seen this before. I'll have to make sure the places I get gas are on this list.
Just FYI, if you buy gas at a Costco that has the 'Clean Power' package, the gas is equivalent to a Top Tier gasoline. Some people would argue it is better, due to the specific additive package and concentration used.
 

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Just a note that the USA/Canada use a different octane rating (MON) to most of the rest of the world which use RON - so the numbers are not the same..

For example, unleaded here is 91 RON, premium is 95 or 98 RON (there are two grades of premium).
 

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Close. North America uses (R+M)/2 so a North American 87 is close to the rest of the world's 91.
 

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Since different brands come from the same refineries, I would go on to say the differences in the same octane ratings of different brands is in the additive packages.
You are in good company, because that's what I've read from MANY sources that are in the fuel business; some were scientists, some were truck drivers. Both report the same practice: the differences are due to the additive packages.

That is why I buy the cheapest, lowest Octane rated fuel I can find (that's 85 here in the mountainous states), and put in my own additives...so I know I'm above the minimum additive pack standards. I learned this from a fellow that does Used Oil Analysis for a living.
 

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Do you really want to know a lot about gasoline? Here's Chevron's "Motor Gasolines Technical Review." It is not self-serving, and it has more than any of us thought we wanted to know about gasoline. It starts off, "In May 1876,
Nicolaus Otto built the first practical four-stroke-cycle internal combustion engine powered by a liquid fuel." and goes on to cover every base after that.
http://www.chevronwithtechron.com/products/documents/69083_motorgas_tech_review.pdf

By the way, we all know the name of a diesel engine, named after Rudolph Diesel and technically called a Diesel cycle engine. Did anyone know that our usual four strokes-per-power-cycle gasoline engines are actually Otto cycle engines?
 

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The recommended grade is in the owners manual or usually posted on a sticker near the fuel cap. Why not just believe the manufacturer?
My 800ST is supposed to use Premium but the owners manual says you can use regular with a drop in performance. I've yet to experience a drop in performance or mpg.
Most of us have no problem with the 650 and regular.
I think the fuel of choice falls into the same category of personal preference as OIL, TIRES and WINDCREENS, oh my!
 

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Octane, again

Octane is the resistance to pre-igniting due to radiated heat in the combustion chamber. Flame travel speed is more a function of gas turbulence (swirl) in the combustion chamber than octane rating. Some relatively high-compression engines get by with regular gas because of superior combustion chamber and intake tract design. Our Suzukis are not included in that group.
 

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Some relatively high-compression engines get by with regular gas because of superior combustion chamber and intake tract design. Our Suzukis are not included in that group.
Meaning of course that they are not high compression so there's no benefit to higher octane regardless of combustion chamber design. Save your money for a cold beer after your ride!


Sent from Motorcycle.com Free App
 

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11.5:1 on the Wee, 11.3:1 on the Vee and 11.2:1 on the Glee aren't exactly low compression engines. My 1975 BMW R90S was 9.5:1 and it required premium. It's more the combustion chamber and air flow characteristics on the Stroms that permit regular fuel than the compression ratio.
 

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Meaning of course that they are not high compression so there's no benefit to higher octane regardless of combustion chamber design. Save your money for a cold beer after your ride!
Modern electronic controls on the engine measure many variables and control the spark timing among other things. The possibility for detonation relates to the load on the engine among other things. Low octane gasoline in a high compression engine is very common these days with the spark way advanced under light load for economy and the spark retarded under high load to avoid detonation. 87 octane gasoline in an engine with 11:1 or 12:1 compression ratio is common. The 2012 Ford Focus 2.0 litre engine has a compression ratio of 12:1 and calls for 87 octane gas, as an example. 160 hp out of 122 cubic inches, very economical, and very clean exhaust.

Engines tuned for high performance and optimized for high octane gasoline will put out more power from the higher priced fuel. They'll generally also run well on lower octane gas (due to adjustments by the electronics) but may burn more so not save any money...fewer miles per gallon of the cheaper gasoline. What really matters when trying to save money is the fuel cost per mile, both the price per gallon or the mpg, not just one or the other.

So...back to our motorcycles. Use any good quality 87 octane (U.S. or Canada) gasoline and have fun. I know that 85 octane is available in the Rocky Mountain states, but that was really for old carbureted engines. Modern electronically controlled engines that call for 87 ought'a do better with 87 at any altitude.
 

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So...back to our motorcycles. Use any good quality 87 octane (U.S. or Canada) gasoline and have fun. I know that 85 octane is available in the Rocky Mountain states, but that was really for old carbureted engines. Modern electronically controlled engines that call for 87 ought'a do better with 87 at any altitude.
My understanding is that, unless you are running a turbocharged engine that keeps the intake air pressure constant, the lower air pressure that comes with higher areas (like Denver Colorado) means that the combustion pressure inside the cylinders is reduced and therefore lower octane gas can be used. Just like there is no octane benefit from using super or mid-grade gas in a DL650 there would be no benefit from using 87 octane in higher altitudes. My 2006 DL650 ran without issue when using the 85 octane out there.

..Tom
 

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I never had a problem with 85 where it was available. It makes sense to me that an engine will have a lower combustion chamber pressure at altitude, the equivalent of a lower compression engine at sea level.
 

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octane mpg compar-o

the proof of how good the pudding is, is in the taste. IOW's, one must do a compar-o to find out which octane 87-89-93, is best for their bike and riding style. thats what i did. i found from my experience that the higher the octane i used, the better my mpg was. with 93 octane giving me the best average mpg. see fuelly link for more info..
 
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