premium gasoline - Page 2 - GL1800Riders
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post #11 of 82 (permalink) Old 04-13-2017, 06:17 AM
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There is almost no limit to the wild claims about octane on both sides of this argument, and most of them are wrong. Too much fuss is made over octane ratings. Octane is a knock index, nothing more. It's all the same fuel. But people just can't resist turning into some kind of magical elixir with mysterious powers. As long as your engine does not ping, you can run any grade your wallet can tolerate. The only time you need to adjust your choice is when your engine pings on a particular octane.

Carbon buildup from high octane is one of the more common myths. On the surface, the theory actually has some merit, except for it to work out, you have to make some assumptions that are wrong, the primary one being the claim of differences in combustion chamber temperatures. Combustion chamber temps don't change with different octane. The same amount of energy is being consumed regardless of how fast the fuel burns. High combustion chamber temps are needed in order to maintain low emissions. If combustion chamber temps dropped with higher octane, emissions would go up, and it has already been proven that there is no difference in emissions with different octane fuel.

There are also some rather amusing contradictions in the claim too. It is said that a slower burning high octane fuel results in incomplete combustion, yet carbon is a byproduct of combustion. Why would there be more carbon from a fuel that is not being completely burned? Not only that, but if the fuel burn was incomplete, fuel mileage would have to drop, which doesn't happen. The argument doesn't stand up to scrutiny on any level.

The theory was debunked a long time ago, but unfortunately still hangs on. It will probably never die. Proponents are right about not using higher octane, but for all the wrong reasons.

Unfortunately, this whole debate is based on the fact that different octanes of fuel don't cost the same. The emotional correlation of higher cost being better is too strong for some. Price overwhelmingly drives our purchasing decisions. I put a lawnmower in my front yard once with a sign on it that said "Works great! FREE." Nobody touched it the whole weekend. Then, at the suggestion of a friend, I asked $25 for it, and it sold in the first hour. It doesn't get any dumber than that.

Last edited by Sparky57; 04-13-2017 at 06:38 AM.
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post #12 of 82 (permalink) Old 04-13-2017, 06:33 AM
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Carbon buildup from high octane is one of the more common myths. On the surface, the theory actually has some merit, except for it to work out, you have to make some assumptions that are wrong, the primary one being the claim of differences in combustion chamber temperatures. Combustion chamber temps don't change with different octane.
Then this one has the folks at Harley Davidson fooled also. When I bought my first Harley back in 2006. I asked why they recommended high test fuel for it when the compression ratio numbers didn't justify it's use. They told me that I was right that it would run just fine on regular fuel but "the motor company recommended using higher octane fuel to keep cylinder head temps down". I didn't own the 2007 model I bought but a little over 600 miles because the 31 days after I took delivery. I rode it 15 of them and it was in the shop for repairs the rest of the time.

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post #13 of 82 (permalink) Old 04-13-2017, 06:47 AM
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Then this one has the folks at Harley Davidson fooled also. When I bought my first Harley back in 2006. I asked why they recommended high test fuel for it when the compression ratio numbers didn't justify it's use. They told me that I was right that it would run just fine on regular fuel but "the motor company recommended using higher octane fuel to keep cylinder head temps down". I didn't own the 2007 model I bought but a little over 600 miles because the 31 days after I took delivery. I rode it 15 of them and it was in the shop for repairs the rest of the time.
Octane requirements are based on many factors. Compression is only one of them. Fuel mixture, and ignition timing advance are two of the more well known ones.

Harley has well known problems with getting its old technology air cooled engines to meet emissions. As a result, they have to use a lean burn strategy. That increases combustion chamber temperatures, which increases the likelihood of pinging. They solve that by increasing the octane requirement. The higher octane doesn't lower the combustion chamber temp. It just allows the engine to withstand it better by increasing its resistance to pinging.

Harley is also often publicly hammered for the low horsepower of their engines, so I imagine they are using the most aggressive ignition advance they possibly can.

Any good salesman will always downplay a prospective buyer's concerns. What salesmen say is rarely based on truth. Harley may actually be telling their dealers this, but they know better.

Last edited by Sparky57; 04-13-2017 at 07:06 AM.
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post #14 of 82 (permalink) Old 04-13-2017, 07:50 AM
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Hmmmmmmmmmmm after reading this post, I may have to discontinue my practice... I always used regular fuel during my regular riding days BUT if I was going on a very long trip I usta always fill tank with premium fuel "thinking" i was cleaning out the injectors and doing the engine good...
Question here: What about fuel injector cleaner added to fuel if on a long trip?
or Startron Enzyme fuel treatment...

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more time to motorcycle and complete the "honey do" list..........
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post #15 of 82 (permalink) Old 04-13-2017, 08:26 AM
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If you have what you feel is a good reason to use a higher octane fuel, then do it. Owners manuals are only a starting point. The are specifically worded as recommendations for a reason.

If I take a trip in the mountains with my trailer and wife, and know that I will be climbing some difficult roads in possible high temperatures that will be placing a larger than normal stress on the engine, then I will use higher octane without giving it a second thought. Engines will often ping when placed under heavier than normal stress. Higher octane can circumvent that temporary anomaly. Doing it just once in awhile under specific circumstances isn't going to be hard on the wallet.

I don't typically buy into the hype of better and more detergents in higher octane, at least to the point where I think it is worth the extra cost. I would rather buy a bottle of Techron once in awhile. But everyone has to decide that one on their own.
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post #16 of 82 (permalink) Old 04-13-2017, 10:11 AM
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I have had a couple of occasions where mine pinged on regular. I think, in each case, it was a bad batch of gas because it is not normal. I normally use a "top tier" brand, whatever that means, Mobil, Shell, Chevron. I do up the octane if I'm in unfamiliar territory and have to use non brand name gas. I don't really care about the cost when I'm on the road.


I have to admit, I think my bike actually runs better on premium fuel......................................just like when it is spotlessly clean and freshly waxed.
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post #17 of 82 (permalink) Old 04-13-2017, 11:19 AM
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http://www.toptiergas.com/

I read the claims for top tier gas and decided to try it in my Ranger pickup. By the third tankful I could definitely tell the engine was running better. Now I will go out of my way to find it. There is a BP station nearby that has ethanol free high test "boat fuel" and I use that in all my yard equipment as well as my motorcycles. Ethanol is very bad for anything with a carburetor and my other bikes are a 1976 and a 1981.
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post #18 of 82 (permalink) Old 04-13-2017, 07:27 PM Thread Starter
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My owners manual says 86 octane or higher.

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post #19 of 82 (permalink) Old 04-13-2017, 08:10 PM
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My owners manual says 86 octane or higher.
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post #20 of 82 (permalink) Old 04-13-2017, 08:41 PM
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