Best Gas Octane to Use?

goodfornothing

goodfornothing

Spicey!
I'm not sure which octane to use for my cb450. The manual says regular but it also says premium, so I'm a bit confused. I understand that higher octane means that the gas is harder to burn, so would gas octane affect starting the bike? Would it also affect or be affected by the air/fuel ratio?
 
Short answer is - the higher octane the better.

Higher octane rating means the gas ignites at a higher temperature - which means it will not pre-ignite (or"pink") in a hot hi-comp engine. It will not affect starting.
 
Not always. I found the SR500 ran better on 91 than 95 or 98. Experimentation is the best way.
 
Staffy said:
Not always. I found the SR500 ran better on 91 than 95 or 98. Experimentation is the best way.
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I found that too sometimes - but it depended on where I bought the fuel. If I went to a busy station, the premium fuels were good. If I went to a not so busy station, the premium fuels were.....not so good. I think it has to do with the age of the fuel at the less busy stations.

For what it's worth, I've been using BP Ultimate on all my bikes for a few years now and it is the best one I've found.
 
I've read that premium leaves carbon deposits on your internals if it's not a high compression engine. When I ran 87, I didn't have carbon soot on my plugs but now they are carbon fouled when I experimented with 91. Is there a correlation?
 
yes.....the higher the octane the harder it is to ignite (you need compression and spark to ignite it more effectively)

personally all i use for fuel for any vehicle is sunoco.....whats te CR on that bike?
 
goodfornothing said:
I've read that premium leaves carbon deposits on your internals if it's not a high compression engine. When I ran 87, I didn't have carbon soot on my plugs but now they are carbon fouled when I experimented with 91. Is there a correlation?
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Was the 87 leaded fuel?
 
Pick a fuel, then tune the bike to it. I run premium in my car and the GS850. The 125 gets 98 octane because it runs horribly without it, and has a 12.5:1 compression ratio.

If you tune your bike to a higher octane fuel you won't regret it.

Cheers - boingk
 
I used unleaded fuel. I think my 450 might have run better on 87. It fired up a lot quicker than when I used 91, and I used the 87 when it hasn't been fired up for 8 months!
 
Wait a minute...didn't know you guys could get 87. Down here the lowest rating is 91, then 95 is premium and 98 is the top stuff. 100 octane is available at some outlets. Do we both use the same rating systems?

Lower ratings will certainly respond better to a given spark (read 'start better') but the general way of adjusting to a fuel making carburettor adjustments via needle taper and height or jetting size. Best starting is given with a strong battery and good quality, modern ignition components.

The best method is to log some dyno time and see what you're able to get with given fuels. This is a major stuff around, though, and requires carb bleeds and the like.

- boingk
 
The factory recommended octane for my CB350 is 91 so I used that for years. Since I switched to Dyna coils, I tried a few tanks of 87 and found that worked better. My plugs stopped fouling and my fuel economy improved without any noticeable loss in performance and I didn't spend as much on fuel.
 
Thank you for this DrJ! My plugs fouled once I experimented with 91, so I'm going to go back to 87. My manual says it recommends 86 (pump), and 91 (research, whatever that means).

Boingk, most gas stations here in CA are rated as 87 (regular), 89 (supreme), 91 (premium). Weird stuff lol.
 
FYI, octane ratings were different back in the day when these manuals were being written. 87 octane back then is like a 91 now. 91 (research or race) then is like the 100+ octane now. Fuels were also leaded then too which effected the octane ratings. Important thing is to tune the bike to the fuel of your choosing.
 
goodfornothing said:
Thank you for this DrJ! My plugs fouled once I experimented with 91, so I'm going to go back to 87. My manual says it recommends 86 (pump), and 91 (research, whatever that means).

Boingk, most gas stations here in CA are rated as 87 (regular), 89 (supreme), 91 (premium). Weird stuff lol.
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Here in australia we have 91, 94/95 (depending on petrol station) and 98 ??? I wonder if ours are rated in a different way but it's the same fuel...
 
Sounds more than likely, staffy, seeing as we are well in the minority when it comes to consumption of fuel and design of vehicles. In other words, I'm pretty sure we get exactly (or almost) the same as the States get.

Hell, even our beloved Holdens are basically rebadged and styled GMC Chevs.

- boingk
 
boingk said:
Hell, even our beloved Holdens are basically rebadged and styled GMC Chevs.

- boingk
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Jeez, you couldn't have got that any more wrong even if you tried ;D

http://www.holden.com.au/corporate/about-holden

Back to the fuel issue, you'll more than likely find the additives in the fuel to obtain the higher octane rating are making carbon deposits, etc.

A question to the US guys running unleaded in the older motors - do you guys run any additives to protect the valve faces? The older engines were designed to run on leaded fuel, yes??
 
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