Honda CBR 250 Forum banner

21 - 40 of 48 Posts

·
Registered
Joined
·
1,105 Posts
OK, for a modded (higher compression) engine it may be required.

Keep in mind if you are looking for the best performance from an engine (like you must be) just running the highest octane gas available is costing you power. You want the lowest octane level that just barely holds-off detonation.

Many moderately tuned race engines will produce more power on pump gas than a high octane race gas, but because the "spec gas" is required they all have to use it.

You need to run the modded engine on a dyno with different fuels to know what is best. Higher isn't better. Proper octane fuel is a simple way to get all of the potential power from a modified engine.
I understand that but I refuse to run gas that has ethenol in it and up here anything other than premium has ethenol.
 

·
Registered
Joined
·
40 Posts
what jkv said. The question I have is, how do you know if the gas has ethanol in it? I've been looking at the pumps, and can't find any indication of a percentage of ethanol.
 

·
Registered
Joined
·
2,038 Posts
I understand that but I refuse to run gas that has ethenol in it and up here anything other than premium has ethenol.
I agree with that - I will use Premium also to get away from Ethanol. In that case it's almost a wash - removing Ethanol will give you some mileage and performance benefits, but the excess octane will cost you some.

Do you have any Cenex stations in your area? The ones around here (south central WI) all have 87 w/o Ethanol.
 

·
Registered
Joined
·
706 Posts
On my bike I got 76.6mpg on 93 and the following tank with the same driving style got 69mpg with 89 octane. So pretty much I'm still sticking to 93
 

·
Registered
Joined
·
112 Posts
IMHO as long as it is 87 octane and up, it should work fine. however, if you are in a long ride and running out of gas soon, you might want to consider getting gas from the nearest station no matter what grade it is and whether its ethanol or not.

even if our CBR250R's are only around 350lbs, its still a pain in the rear to push it for miles if you run out of gas.:D
 

·
Registered
Joined
·
2,038 Posts
On my bike I got 76.6mpg on 93 and the following tank with the same driving style got 69mpg with 89 octane. So pretty much I'm still sticking to 93
It may be possible that the 93 didn't have Ethanol and the 89 did - that would explain the increase in mileage. The higher octane works against you, but you still come out slightly ahead without Ethanol. I'll bet that's the reason for the increased mileage. 87 without Ethanol gives you the best of everything, but its not always available.

The only time a high octane gas would be necessary is if the conditions caused you to detonate on 87.

In normal conditions, there is absolutely, positively, no performance or mileage increase with more octane than needed - it kills power!
 

·
Registered
Joined
·
1,401 Posts
On my bike I got 76.6mpg on 93 and the following tank with the same driving style got 69mpg with 89 octane. So pretty much I'm still sticking to 93
I would try more than just 1 tank...i actually got better gas mileage from the lower octane with the exact same driving styles.....exact opposite of you...did it have anything to do with the gas?...maybe/maybe not
 

·
Registered
Joined
·
27 Posts
From what I heard the manual says to run 87 octane but I've been running 89 for kicks and gigs but today I decided to use 93. And i was able to break 80+ with relative ease. Whereas before it would struggle to reach 80.
 

·
Super Moderator
Joined
·
2,049 Posts
Colder air is denser and has more oxygen. All bikes perform better (once the engine is warmed up) at colder temperatures. Could this be a factor in your comparison?

The CBR250R engine has a 10.7:1 compression ratio. It shouldn't need a premium fuel to prevent premature detonation.
 
  • Like
Reactions: Figlamic

·
Registered
Joined
·
68 Posts
Colder air is denser and has more oxygen. All bikes perform better (once the engine is warmed up) at colder temperatures. Could this be a factor in your comparison?

The CBR250R engine has a 10.7:1 compression ratio. It shouldn't need a premium fuel to prevent premature detonation.
Would the ECU adjust for the colder temps? This is a question I have wondered about. BTW, mine seems to run about the same. Seems is the key word.
 

·
Registered
Joined
·
514 Posts
Can't really talk about 'cold' air.
But there seems to be a difference, from 30+ degree centi., to just about 24/25 degree, on my bike.
To the 'a bit better'.
But it's maybe more the less water in colder air (in your areas).
 

·
Registered
Joined
·
3,226 Posts
engines will function better in colder air
as its then denser, thus 'more of it gets in'..

early morning and cool night
are 'better' for my motorcycles..

higher octane number petrol does not mean better,
in terms of performance.. higher compression ratio
engines,, require higher octane number petrol to avoid
pre-ignition [knock] thus potentially damaging burning
conditions within their combustion chamber..
the idea that higher octane means higher
performance is just that, a wrong idea..

this engine as members note has a relatively low cr
which has been designed around a certain flame throw
and burning rate or pattern, for best performance etc..
higher octane petrol has different but not 'better'
burning pattern in our engine so cant be 'better'..

in emergencies i have used higher octane petrol
to avoid running out and to avoid ethanol..
here [sydney aust] shell petrol at our octane
had ethanol so i filled up with 97 or 95RON
"premium" petrol.. didnt seem much difference
if any in general suburban type riding..
including 'test riding' attitudes etc..

this engine has been designed to run on 91RON [87PON]
so unless you want to pay for the additive package in
'premium' [as in 'higher price'] petrol, then 91RON
[87PON] should be your petrol of choice..
and without btu ths power and fuel efficiency
lowering, ethanol, if availably..

- sydneysiders,, the caltex on maroubra road
south of coogee has no ethanol in their petrol
including 91RON -

this topic has been well, covered here..
simply go to the search box..
 

·
Registered
Joined
·
1,109 Posts
I wrote a post on this exact thing: Regular Fuel vs. Premium Fuel Myths

Basically use what the manual recommends. The 250 here requires 91RON. There is no need or point to run 95RON or 98RON.
 

·
Registered
Joined
·
409 Posts
93 Octane.

Here, California, we have Ethanol. Usually 5-10% (but they are not required by law to tell you how much, could be 15%). I always dose mine with Seafoam fuel stabilizer after I fill up. Strictly speaking it may not be necessary but my bike may sit for a few weeks between rides in spite of my best intentions.

I get my best, smoothest performance right after I fill up (top up, at least 1.5 gallons [5-6 liters]) with 93 octane and the engine is warmed up (after riding several miles). It runs fine after sitting for a few weeks, just not as smooth. I try not to let it sit for any long period with a less than full tank.

One of the things that sold me on this bike was that it was fuel injected and had no 'special' fuel requirements. Still, I understand. You ride enough you get attuned to how your bike feels. You can tell if it is running a little 'rougher' on a particular fuel.
 

·
Registered
Joined
·
163 Posts
The U.S. owners manual states to use 87 octane gas. The 250R is not a high compression engine. Using anything more than 87 is just a waste of money. Some folks think octane is an additive (not on this forum of course!) but it's simply a rating. Some high compression engines will knock with 87 octane gas. This is because high octane gas is actually less combustable than lower octane. So, with our 250's not having high compression needs it will run better and save you money to use the low octane gas.
 
21 - 40 of 48 Posts
Top