I run 93 in mine. I put 89 in it once which is typical midgrade around here and I went from getting 130 miles to a tank to right At 100. So ever since I just run 93 plus while it had 89 in it it wasn't as peppy as usual.

This is directly from the F4i Manual, Its says your engine is designed for ANY gas with an Octane level of 86 or more.


Type: unleaded
Pump octane: number 86 (or higher)

We recommendth at you use unleaded fuel because it produces fewer engine deposits and extends the life of exhaust system components.
California only:

The use of leaded gas will damage the catalvtic converter.
Your engine is designed to use any gasoline that has a pump octane number of 86 or higher. Gasoline pumps at service stations normally display the pump octane number.

Use of lower octane gasoline can cause persistent "pinging" or "spark knocking (a loud rapping noise) which, if severe can lead to engine damage. Light pinging experienced while operating under a heavy load, such as climbing a hill, is no cause for concern.
If pinging or spark knock occurs at a steady engine speed under normal load, change brands of gasoline. If pinging or sparkk nock persists consult your Honda dealer.

Bull****. I've been a service writer at a honda motorcycle dealership for a long time. I read several f4i manuals from 01 to my 06. Your bike requires 87octane. As I said, the sticker on the bike saying 91 is the RON/europian rating, the manual stating 87 is the AKI/american rating.

Jeffjones- it says any grade higher then 86 because anything less will cause actual physical damage to the engine while anything higher will only cause slight performance reduction but the engine will be fine.

Uh, no it doesn't. I never said I have an F4i. I own an 08 1000RR. It requires 91 octane minimum, as stated in my owner's manual.

Well I guess everyone assumed you had a F4i since your posting in the F4i section.
You should have mentioned that you have a different bike and manual then everyone else in here.

I was merely surfing the forums via the 'New Posts' button. The title of this thread caught my attention. Didn't really notice or care what section it was posted in. My reply had to do with following the recommendation of whatever it says in your owner's manual as far as what octane to use.

:icon_lurk5:

Oh my God.

I HATE this topic.

Octane is just a level of when the fuel will ignite. You get more power by running the lowest possible octane possible for your power / timing condition.

Unless you have advanced timing or power adder (supercharge / nitrous / turbo whatever) you need to use what is recommended for your vehicle. (so if it says min 91 octance - then 91 or higher, but putting cam 2 - which is race fuel 110oct - in your bike is only gonna hurt.)

This is true of all engines - vehicles / bikes etc.

Running too high of an octane for your condition will lead to fuel deposits because the higher octane fuels burn slower than a lower octane.

:icon_slap: not that any of this will help the argument, but its all true.

I've had a 5.0 mustang with a Votech S-Trim and a 50 shot of Nitrous as an intercooler, a '95 bottle fed 5.0 and a full bolt on LS1 T/A. I know a thing or two what i'm talking about.

With that said -
The pump thing is quite interesting. I'd like to see some studies done. I wonder how much does actually stay in the line.

This topic is really beaten to death -

As a general rule you should only use what your manual says!

For the average person with an F4i, using a higher octane isn't going to really damage the engine, but it won't help either. Anyone who puts a higher octane in their F4i thinking they are going to get better performance is sadly mistaken.



And let me be the first to predict this - within 2 weeks someone will start another thread talking about the same thing.:icon_gunhead:

Thanks for everyones input. The good news is now I can start using 87 octane. I guess not everyone understood my question. I just wanted to know, how much fuel is left in the line before get fill up with the selected octane?