Hey guys, this question has probably been asked a bunch of times but what octane rating do you guys run in your F4's? I have been running 91 and just was curious what others ran.

 

87 is sufficient.

 

The only reason to run 91 is if you hear a engine knock.
Other than that the engine was designed for 87 so you will most likely get the best performance from that along with longevity of the engine.
If they wanted people to run 91 they would have put it in the manual.
No need to spend the extra money

 

I run 93 in mine.. higher octane burns cleaner so is 'better' for your engine, but it wont give much of a power boost even though most ppl think so...

and engine octane rating is based on compression ratio and only means that u have to put at least that octane in order to prevent premature ignition (anti-knocking) so it is alright to put something higher in

 

On the 2006 600RR it recommends 86 octane or higher. That must be the same for the F4i. If it doesn't run well with 87, check and make sure the O2 is connected (is aftermarket exhaust is present) You can get a O2 bung welded on the mid section pipe. Some people say that the O2 sensor does not make a big difference but I don't believe that is true. OEM don't usually add components is they are not required.