[D dot T]

87 majority of the time and 91 once in a while for the extra detergents they offer to clean out the engine.

[allblackkat]

There's a great thread on Kat octane here:
http://www.katriders.com/forums/viewtopic.php?t=5574.

Covers all the bases, the why and wherefore, when you do need higher octane fuels and when you don't, etc.

PS - No E85!

Cheers,
=-= The CyberPoet

Yeah plz no E85.

DOH!

[efozie]

I just use 89 octane...got the ignition advancer and don't want to run the engine on the low grade...after reading the post I made a good decision for a newb

[99CBRHalleck]

I thought because of the compression you should always use premium

[TheCandyman]

Nope. 87 is what you want to use. For every bike i have owned from a Honda Rebel to a CBR To a Katana i have always put in 87 octane

[Sixpoint]

Yep, if your engine will stand it (and most will, unless like SweetLou pointed out you have serious engine mods) - if your engine will stand it, there is fractionally more horsepower (and fuel mileage) in 87 octane than in 91 or 93. The octane rating is basically gasoline's resistance to detonation (pinging, etc.), which means, in essence, that it is less explosive. So, unless you have increased your compression ratio, altered your timing, or otherwise affected cylinder pressures, 87 works just fine.

[2000kat600]

I've got a 2K 600, used the highest octane available the first year 'cause the dealer guy said so then for the last 4 years up-to-date I've been using the least octane available which is 87 here in CA,,, and some unknown unledded Cow-Pee from Tijuana, Mexico a couple times years back...

[ArnhemKnight117]

I have a 1990 katana 750, and i was told to always use the premium stuff, but apparently thats a myth, and now is idling kinda low... i tried adjusting the idle screw but its still doing it. I thought maybe the carbs or air filter was dirty, but could it be the grade of fuel?

[The CyberPoet]

I have a 1990 katana 750, and i was told to always use the premium stuff, but apparently thats a myth, and now is idling kinda low... i tried adjusting the idle screw but its still doing it. I thought maybe the carbs or air filter was dirty, but could it be the grade of fuel?

Although colder weather will cause initial idle to be lower, it won't affect warm idle. From the sounds of it, it's more likely it's dirty fuel passages. Try running some fuel system cleaner (techron) through the bike.

Cheers,
=-= The CyberPoet

[95Kat]

I was always told to use premium also but everyone seems to be doing good with 87 I think i'll try it

[ArnhemKnight117]

Thanks cyber poet

[BlackburnD]

For anyone thinking of going back down a grade or two if you are using higher octane fuel you may want to rethink that or atleast do it slowly. Like if you are using 91 drop down a grade at a time. In my experience working on cars and being an engine specialist it has been found that dropping down fuel grades once you have been using higher fuel grades can cause what is known as spark knock. Basically it's a pre combustion problem. For some odd reason engines get used to running the higher octane and it causes some goofy issues. I am not 100% sure that this will be a problem with motorcycle engines, but I just wanted to throw that out there if anyone experiences this issue after switching fuel grades. This does not generally happen when switching from a lower to a higher octane fuel though.

[loudnlow7484]

I swear on my life, there was a sticker under the seat, on the inner fender of my last 750 that said to use at least 91 octane fuel in it. Anybody else with a pre98 750 have that sticker?

[Kataclysm]

BlackBurnD; I believe going down a grade only affects vehicles that have computer controlled fuel and ignition systems.

Going through the 98+ Kat 600 manual it says to use 91 or higher.. ????

[The CyberPoet]

RON vs. PON

In countries that use RON as the octane rating, 91 is called for.

In countries that use PON (calculated as [MON+RON]/2 = PON), 87 is called for, which is equivilent to what you would expect from a 91 RON fuel.

Cheers,
=-= The CyberPoet