98 Octane Fuel

[eddohawk]

Hello and a very happy new year to everyone

I was wondering if there are any potential problems if I use 98 octane fuel?  A friend suggests that running a single tank load of higher octane fuel can be beneficial in burning off excess carbon build up and cleaning carbys and fuel lines.  Whilst my recently acquired FJ starts and runs 'ok' it does feel sluggish and an inspection of the plugs has revealed it is running rich. High fuel consumption could also be an issue but I dont have any consumption data yet. After I finnish checking the valve clearances, synching the carbs, changing plugs and the air filter my next thought is to give the bike a decent workout on 98 octane. Would be interested in anyones opinion of whether this is a good move.

Regards

Mark

[RACER111V]

 The simple answer is you want to run the lowest octane that you can without detonation.High octane fuels can actually add to carbon build up.A high octane fuel will not improve or clean any part of your fuel system.

[carsick]

OK, I'll bite- It might feel better because you paid more! No benefit from running higher octane fuel regarding cleaning of the fuel system or motor. Higher octane (in the US) uses more detergents to offset the fact that they create more carbon deposits. I'm not sure what to make of this Oz 98 octane, is it rated differently than the US (Research + motor octane/2) ? You're going to have to teardown the carbs, clean them ultrasonically, replace worn bits and tune properly if there is a fuel calibration problem. Unless it's a petcock, filter, pump, fuel line routing, or leaky carb boots causing a lean mix. Lean misfire can leave plugs dark and wet, not just rich mixtures. The only snake oil in a bottle I know of that works on gum and carbon from personal experience is Chevron Techron CONCENTRATE. They make a diluted "fuel system cleaner" that is much weaker but looks similar.
Doug

[andyb]

As long as it doesn't detonate, one tank isn't going to hurt anything, unless it's got crazy solvents eating the rubber bits or is so terribly oxygenated that it runs you lean.  Instead of futzing with the fuel, why not fix the richness by adjusting the carbs properly?

If it's the detergents you're after, dump some trans fluid, seafoam, or whatever you prefer in your fuel.

[bcguide]

I ran the cheapest fue lI could get in my fj in 90000 kms 2 months in Mexico and it was still running well when I parked it because of 2nd gear isues

Scott

[roverfj1200]

Fuels and oil threads Mmmm..

My 2C.... I run E10 when ever I can get it and have done now for close on a 100k(most fill ups)... with no harm to the bike that I can see. and I feel the FJ enjoys the 95 octane to..

Cheers

[Harvy]

Fuels and oil threads Mmmm..

My 2C.... I run E10 when ever I can get it and have done now for close on a 100k(most fill ups)... with no harm to the bike that I can see. and I feel the FJ enjoys the 95 octane to..

Cheers

Rover......I concur with the E10, tho I don't use it all that often...... usually just stick with common or garden variety 91 octane.

Harvy

[SkyFive]

If a FJ was detonating how would you hear it above all the other engine noises?  

I would suggest reading up on reading your spark plugs. I was surprised at what they reveal about your combustion and mixture.

[elbows]

in the UK it sounds like the fuel we use is much better than you have, 98 is all i ever use with no problems have ran 105 much better with the ignition avancer is even better mind that was some old race fuel that was kicking around after the race season had finished  the bike pulls much better on the old race fuel, and a little better on MPG, but had to tell as i was giving it some stick at the time, so is the reason you find that the ignition avancer don't work for you ,
as the fuel you use is not quite as good as the stuff we use in the UK

[Dan Filetti]

in the UK it sounds like the fuel we use is much better than you have, 98 is all i ever use with no problems have ran 105 much better with the ignition advancer <snip>
as the fuel you use is not quite as good as the stuff we use in the UK

You may be right, we oxygenate, and add nearly-useless ethanol to a lot of our fuels here in the US.  It's a fairly ridiculous patronage to the farm industry, stillborn from nation politicking and the inherent demographic inequity of the Electoral Collage. -But I digress...  Also I'm pretty sure there is a difference in the octane ratings themselves between the US and the UK. So "105 octane" in the UK is a different animal than "105 octane" here in the US.

But, I seem to remember that you folks pay an awful lot more (2:1, 3:1?) than we pay in the US. -So, you get what you pay for?

Dan

[Travis398]

But, I seem to remember that you folks pay an awful lot more (2:1, 3:1?) than we pay in the US. -So, you get what you pay for?
Dan

that may change in the next year or two.

[weymouth399]

that may change in the next year or two.

Ya we will pay big money for crap fuel, lucky us. 
E10 (closer to E20 actually) is the biggest joke going on right now in the US. All it does is fuck shit up, we can't grow enough corn to be a suitable replacement to gas, takes a third more fuel to do the same as a gallon of gas. 
Ya thats worth it 
Bob W

[Dan Filetti]

that may change in the next year or two.

I wonder.  Net net, a barrel of oil remains measured in USD, and the greenback, despite quantitative easing, is still highly valued in the world.

[andyb]

Also I'm pretty sure there is a difference in the octane ratings themselves between the US and the UK. So "105 octane" in the UK is a different animal than "105 octane" here in the US.

http://en.wikipedia.org/wiki/Octane_rating#Regional_variations

In the UK, RON is the number the pump reads(?).  In the US, the AKI is used ((RON+MON)/2).

98 octane in the UK, i.e., Shell SuperPlus, would be rated at 93-94 in the US.
Australian gas listed as 91 octane would be listed as 87 in the US.

A typical pump in my area sells 87, 89, and 91.  Now I'm going to have to go and see what the RON's are for them, fooey!  I do understand that the typical pump of UK fuel would be labelled as 89, 91, 94 if it was under US law, so it's still a pinch higher octane.  Seeing as most motorcycles that I'm aware of use the same compression ratios between the two markets, I'm not entirely sure that it's "better" fuel, as you're paying for lower performance comparatively.  Now, if there's a machine that won't run on 87 AKI fuel, then they'd be equal (as the US would have to use a mid-grade).  If there was something that I couldn't get to run well on 91 AKI (standard high-test at my local pump) without knocking, then the other fuels would be decidedly superior if they could run it without detonation.


If you want really good gas, you buy it at a race track, not at a common or garden pump.  And it's usually a waste of time and money, unless it's highly oxygenated and you've tuned for it.  Not uncommon to spend $100 on a 5 gallon can of good fuel!

[Flying Scotsman]

One of my Gp1200's runs on 98 octane due to raised comp ported cylinders etc I buy either 100 or 110 octane pump gas and blend it with 93 octane pump gas.It costs about 1/3 of the cost of vp race fuel in the can.Runing high octane gas in a low compresion motor just slows you down a little it wont burn right in the combustion chamber so it wont make max power.The main reason to use high octane is high compresion.Put high comp pistons in your motor and you will need to run higher octane.You will make more power then as well.