there will be arguments either way, some with science, and some without. all i can give is my personal experience, and that is that no matter what you put in it, try to get ethanol free. i always run 91, no matter what, but if i can make it to a station that has it, ethanol free is the way to go.
A lot of people say that using high octane fuel in a low compression engine won't do any harm and just waste's money; but I would disagree.
High octane fuel can cause carbon build-up when used in a low compression engine. The higher octane rating is used to keep the fuel from igniting too soon in a high compression engine.
The higher the octane number, the more compression the fuel can withstand before detonating. In our low compression engines, 91 octane is not needed. It's a waste of money and doesn't help performance.
A lot of people say that using high octane fuel in a low compression engine won't do any harm and just waste's money; but I would disagree.
High octane fuel can cause carbon build-up when used in a low compression engine. The higher octane rating is used to keep the fuel from igniting too soon in a high compression engine.
The higher the octane number, the more compression the fuel can withstand before detonating. In our low compression engines, 91 octane is not needed. It's a waste of money and doesn't help performance.
***I second gypsy's suggestion about the FUELOLOGY sticky in the tech section.
So many folks think octane is a power boost of some sort.
The other side of what Phil is talking about is that using a higher octane fuel will hide carbon build up and other heat issues in the combustion chamber. I almost learned an expensive lesson (engine rebuild) by using higher octane fuel.
Here's why: With carbon build up on the piston, the piston gets and remains much hotter than it should. When the fuel/air mix enters the combustion chamber part of it ignites from the heat on the top of the piston. Once the spark plug fires, the two flame fronts collide as the piston reaches TDC and pinging and knocking are the result.
A plug with too high of a heat range or poorly adjusted valves can also provide enough heat to cause the fuel/air to ignite.
A higher octane fuel requires a higher temperature to ignite the fuel/air mix so using a higher octane will indeed stop the pinging and may eliminate power loss from the fuel burning improperly. (This is the perceived 'performance boost' some claim to get from higher octane.) But it hides any carbon issues, valve issues or spark plug issues....(heat sources)
The best way to help your engine is to make sure you run the correct heat range plugs, keep the valves in spec, and run some type of carbon cleaner once in awhile.
I use Techtron. I was getting some pinging so I bumped up to 89 octane, then did some research on pinging and the carbon build up issue was mentioned. I ran the Techtron through the bike and did some highway runs to open it up. Switched back to 87 octane and after a few tanks the bike runs great on an octane the engine was made to handle. I dump some in the tank a few times a year and have better mileage, and the engine runs better on 87 octane.
BTW....Techtron, Startron, and similar products are fuels themselves so you can't overdose except to waste the stuff. Additives such as Seafoam are a different animal and don't really work as well in this instance.
In Australia the lowest octane fuel available is 91octane and is also available in 95 & 97 Octane.
I mainly use 91 but every now and again if I'm going to go for a blast up through the hills when I'll be on and off the throttle, I'd put 97 in it.
It doesn't hurt anything using the higher octane but if you're just cruzin' around it is a waste of money...
Ran 91-92 octane for years. Read a good write up on octane and switched to 87 octane. Now it starts and runs better. Look for a thread or a sticky on here I'm sure there is one and you can make an informed decision.
Yep, fuelology sticky on technical discussion thread. Kinda deep for me but its good.
No need in using higher octane with Ethenal is it? You are just paying more for less gas right? It seems to make no performance upgrade on the ethenal fuel, so, I wont buy it. But the VTX is recommended low octane, and it is happy with it. I run No ethenal all I can and the mileage IS better by almost 2 MPG when I drive nicely.
Coop
Ethanol actully will give regular gasoline increased octane rating. It also burns "cooler" and cleaner. However, more fuel is required with enthanol as stoich is at a lower a/f ratio compared to gasoline, something like 30% more fuel is needed when using e85. But, our bikes won't run on e85 out of the box without a fuel system replacement and the amount put in regular gas is so negligible that you won't see the increased octane rating or cooler burning.
I run what the manufacturer says. 87 in the bike Premium in the Taco. 87 will run in the Tacoma but I noticed (using fuelly.com )the fuel mileage does go down. I don;t drive it enough to worry about MPG. 4500 miles a year maybe.
I find my fuel injected 1300 runs better on the 87 octane than the premium. No issues with the ethanol. But my lawn equipment and snowblower run better on the premium.
If your user manual says use 87 use 87, period.
The octane ratine (say 87) is where the detonation range is.
If you put 91 into an engine made for 87 the detonation will occur in the 91 octane range, not in "that" engine's sweet spot of 87.
Old engines which were rated for 87 but developed a "pinging" sound have carbon buildup which increases the compression due to less air expansion room from that carbon buildup.
To get rid of the pinging mechanics will tell you to put a higher octane fuel in, which - with the higher octane rated for higher compression engines - matches the new compression ratio (due to carbon buildup) to a higher octane,
So if your engine does Indeed run better on higher octane vs what its manual states, then it has bigger problems besides costing you more at the pump.
Anything else is marketing hype & or perceived seat of pants "pep".
As far as detergents, they all have them.
Use what your manual states for best results.
Long before there is enough carbon to effectively change the compression ratio, what carbon there is will prevent the piston from cooling. The carbon gets hot, stays hot and ignites the fuel/air mix at the top of the piston before it reaches TDC. (Think charcoal in a grill glowing red hot). That flame front moves up and hits the flame front caused when the spark plug goes off and causes the knocking and pinging. Same thing happens if you have a plug with too high a heat range, or a valve (usually exhaust) that gets too hot.
The responses I have gotten to this question are exactly the reason I like this forum. I am admittedly under educated when it comes to things like this, although I am working on learning much more about my bike and the things that cause good or bad performance. Thanks to all of you
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I am no fuel expert but I have spent some time researching this question. Octane is a rating pertaining to the fuel's ability to prevent detonation. An engine with a higher compression ratio requires more octane to prevent detonation. If your engine requires lower octane fuel then running higher octane fuel is just throwing money to the petroleum companies. If you maintain your machine then run what the manufacturer recommends.
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