Gas types in a bike.

[Obviouslykk]

Hey guys,
Im curious, and havent been able to find any straight answers yet. What is the difference between 91 octane and Ethanol gases. and why is it "not accepted" in bikes. Ive been seeing alot of cars using e85. in their cars. maybe im just not fully understanding the difference and the purpose of the two.

[got2go]

e85 (85% ethanol/15% gasoline) can cause corrosion of aluminum parts and decay of rubber parts.
It has a higher octane than gasoline, but less energy per unit (this translates into lower MPG, all other things being equal).

Basically, unless your engine was designed to use e85, don't use it.
Use the lowest octane fuel where the engine doesn't ping/knock...that will give you the best performance.

Example: If manufacturer specifies 91 octane, you should be able to use 89 octane at our altitude (LV) as your engine will never achieve the cylinder pressures it would at sea level (where the octane ratings are specified).

[the falcon]

(05-19-2014 05:25 PM)got2go Wrote:  e85 (85% ethanol/15% gasoline) can cause corrosion of aluminum parts and decay of rubber parts.
It has a higher octane than gasoline, but less energy per unit (this translates into lower MPG, all other things being equal).

Basically, unless your engine was designed to use e85, don't use it.
Use the lowest octane fuel where the engine doesn't ping/knock...that will give you the best performance.

Example: If manufacturer specifies 91 octane, you should be able to use 89 octane at our altitude (LV) as your engine will never achieve the cylinder pressures it would at sea level (where the octane ratings are specified).

What he said. I second the motion

[Obviouslykk]

Yeah i figured to stick with 91 octane on my bike. i was just curious about the difference

I just see so many diff cars/bikes using different fuels so it made me curious. Thanks for the reply!

[Dougk35]

Isn't it 85% gas 15% ethanol? That's what I thought anyway.

[Dougk35]

(05-19-2014 06:58 PM)Dougk35 Wrote:  Isn't it 85% gas 15% ethanol? That's what I thought anyway.

I'm wrong. 85% ethanol 15% gas.

[Rev. That Guy]

Basically what got2go said was correct! E85 is 85% ethanol. DO NOT use it in a motor that was not designed for it. It burns much cooler and produces significantly less energy than its gasoline counterpart and motors have to be specifically designed for its use. Ethanol molecules are much larger than straight gasoline and thus different injectors or jetting must be used to compensate and maintain proper fuel/air mixture. Further, any alcohol based fuels have a tendency to dry and destroy rubber seals and so engines designed for it have a different type of compound in the engine seals that can handle it.

One major advantage to ethanol, although not really applicable here, is that it wont detonate like gasoline will and because of this, it makes an excellent choice for a fuel conversion on higher performance boosted vehicles. I have seen Subaru WRX's converted to run E85 and are making 17-22psi of boost with no problems. The lack of detonation means less ignition retardation and more power output. It also burns cooler and this is a bonus for forced induction vehicles to keep engine temps in check.

For a motorcycle, however, it will likely depend on your bike specifically. In my bikes (02 FI RC51, 84 Carb'd VF1100C Magna and an 06 Carb'd EX500) I run 87 octane with ZERO issues. I have had no problems with ping/knock (detonation) and no power or fuel economy issues (other than my heavy wrist). I did, however, have a 95 CBR600F3 that WOULD NOT even start of anything less than 89. It was a race built motor though. I get SLIGHTLY better fuel economy with mid-grade, but not enough to make it financially worth while (about 0.5 - 1.0 MPG average for similar riding conditions).

you have an FI 600. Use the cheap stuff. No need to spend the extra money on premium. You wont net anything positive from it.

The rule of thumb is that about 11-12:1 compression is the magic number. Below 11:1 or so you don.t need premium. Above that, you run the risk of detonation without a higher grade gasoline. Even still, Unless you are talking about a high performance built motor of forced induction, you still dont really need the premium unless knock is real bad. In a naturally aspirated motor, knock isnt really going to hurt much of anything as it just doesn't have the compression to be dangerous. In a boosted vehicle, detonation sends engine cylinder heads through hoods. You may loose a touch of power if you have a little detonation, switch up to the next higher grade. Higher octane gasoline actually contains less energy and burns slower and is harder to ignite (hence the reduction in detonation).

Ultimately, the QUALITY of the fuel is more important than the octane rating. use a trusted, quality source with the least amount a of ethanol as possible. Keep in mind that most fuel available contains at least 10% ethanol and is usually stated as such on the pump. Try and find fuel with less as that is the least damaging to a motor. Often, in winter, the ethanol content will be higher than in summer. Not so much an issue here in the desert, but in colder climates, it can be. This is for a few reasons, freeze (gelling) protection, water absorption, ect.

Lastly, Your manual likely states a minimum octane rating of 91 (R or R.O.N. or RON or Research Octane Number) or something along those lines. This is different than what is used in US gas pumps. US gas pumps use the (R+M / 2) which is an average of the other 2 types of octane ratings (most commonly R.O.N. and also M.O.N.) used globally. Both methods measure differently. 91 RON octane fuel is about the same as 85-86 octane fuel calculated by the R+M / 2 method used in the US. RON is used in Japan most of the rest of the world and so the manuals for most, if not all imports will list this rating.

use low octane and save the extra buck or 2 on each fill up.

- Justin