After reading a post about a brand new Rebel 1100 having black smoke coming out from their exhaust and blamed it from low oil there was no comment on what grade of gas they were using. Some might think its a waste of money to use either 91-93 octane, however thats what I use in both the Rebel 500 & 1100. So far no issues. What octane of gas do you run in your Rebel?
What Octane of gas do you use in your Rebel?
Redshield
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Actually ethanol does not increase HP. It allows for a higher compression which does increase power output of the engine. The compression is to low on engines running gasoline therefore there is less power output from having ethanol in the gasoline. See the wiki quote below.
"Ethanol contains approximately 34% less energy per unit volume than gasoline, and therefore in theory, burning pure ethanol in a vehicle reduces range per unit measure by 34%, given the same fuel economy, compared to burning pure gasoline. However, since ethanol has a higher octane rating, the engine can be made more efficient by raising its compression ratio."
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Sonwon, you're talking about higher octane but that's not what jdock is referring to. Ethanol gives power to an unmodified engine because it adds oxygen. It only needs a richer AFR to make up for the lesser amount of pure hydrocarbons that it displaces. Same is true for any oxygenant. It looks like a stock Rebel does run rich enough up thru the mid range according the measured AFR. Most bikes are a little rich at full throttle and might see the same benefit. If fueling isn't rich enough, E0 would make more power.
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Tuning for today's oxygenated fuels | Fuel Facts
Here is how to tune your classic car to run on oxygenated fuels like E10.
classicmotorsports.com
Thank you for the clarification, in my defense nowhere was oxygenanted mentioned. And as you pointed out this relies on a rich fuel mixture which was also not mentioned. I suppose if it is rich enough it could work however modern engines are designed to run lean to reduce emissions. I doubt the Rebel 500 would be rich enough to benefit from E10. I admit I have never seen a fuel map for a stock Rebel 500. Do you have one?
In personal test in cars E0 tends to provide a little better fuel mileage. I run E5 in an 1100 since the E0 is more than double the price and is very hard to find. I know my Sportster runs better with E5 than E10. E10 gave it this odd stumble when really hot, likely a problem with air cooling over water cooling, the ECM didn't properly adjust to E10, just the fact E10 burns hotter, or all of the above. The E10 did meet the knock requirements of the Sportster. I also like having a little less corrosion water sucking fuel in the tank so I use E5 in all my bikes.
Methanol is what race engines use, either straight or mixed with pump gas. It also milks up the oil very quickly, meaning it has to be changed often.
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The O2 sensor is used to control AFR at idle and cruise automatically so that gets adjusted to around 14.2:1 for E10. As revs go up and loads increase, manufacturers tend to keep things pretty much on the increasingly too rich side. That's according to various dyno charts that show AFR. What I'd like to know is the ethanol content used. Here's one for the CB500:
![Image]()
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The engineers who designed the engine and the EFI system know more bout engine design in general and your Honda Rebel engine in particular compared to we all in this forum. Not only they designed the system, but they had to test every parameter to make sure they'll have the least amount of warranty claims under normal operating conditions. I would listen to what they recommend.
In my Honda Rebel 1100, they recommend using a fuel with at least 86 octanes and maximum 10% ethanol. In the U.S., the cheapest unleaded gas is 87 E10. Any performance gains from using a higher octane or lower ethanol content will not offset the increased cost. I would recommend everyone to save some money and follow the manufacturer recommendations (unless you are tunning your engine to different parameters, but that's a different story).
The only exception is when the bike will sit unused for more than 30 days. Ethanol is hygroscopic. It adsorbs water (different from absorption) which means it attracts water. That water corrodes metal parts. Ethanol also increases the level of oxygen in the gas, which turns the paraffins and other gasoline molecules into a gel. That gums up the ejectors and other components. In summary, ethanol-containing gas sitting in the bike for more than 30 days is a big no-no. You should add stabilizers or use ethanol-free gas whenever you will not use all the gas in the tank within a 30-days period.
In my Honda Rebel 1100, they recommend using a fuel with at least 86 octanes and maximum 10% ethanol. In the U.S., the cheapest unleaded gas is 87 E10. Any performance gains from using a higher octane or lower ethanol content will not offset the increased cost. I would recommend everyone to save some money and follow the manufacturer recommendations (unless you are tunning your engine to different parameters, but that's a different story).
The only exception is when the bike will sit unused for more than 30 days. Ethanol is hygroscopic. It adsorbs water (different from absorption) which means it attracts water. That water corrodes metal parts. Ethanol also increases the level of oxygen in the gas, which turns the paraffins and other gasoline molecules into a gel. That gums up the ejectors and other components. In summary, ethanol-containing gas sitting in the bike for more than 30 days is a big no-no. You should add stabilizers or use ethanol-free gas whenever you will not use all the gas in the tank within a 30-days period.
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lol ive never considered that. so true though.
That's right the engine is designed to meet reliability and emissions. Me and everyone else don't give a rat's arse about emission and reliability. We went more power.
More octane doesn't equal more power...
to get the best of the octane increase, your engine needs to be tuned for it. and it's also to stop knocking or pinging.
Right, for any engine that actually needs it. Your bike tuned for higher octane fuel?
None of the Rebels have high enough compression to worry about knock/ping when running regular fuel.
my rebel isn't but my rm65 and KLX250 are. plus i am over have 3 different jerry cans of fuel just for each machine. a couple of cents difference is not going to hurt the bank.
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