type of gas?

[duma]

i have a gs500 F 2004 and i wanna know if using the 87 type of gas is good?  the manual says to use it, but im just wondering if there is a better type of gas, like the 89 and such?  sorry if i sound stupid... thank you though.

[Ry_Guy]

I've had bike mechanics tell me 87 octane works good in any carbureted bike, even though my manual (96 gs) suggests 91 octane minimum.  :dunno:  But I still use 91 anyways, just cause I want the best for my baby.

[70 Cam Guy]

87 is fine for most people from what I've heard.  I've experiemented a little bit and have found that I get the best mileage/performance on my '90 using 89/midgrade.  However, your YMMV since it's newer and has different carbs than mine.

[Mk1inCali]

I used to run 87 exclusively, but after I put in Bob B's  ignition advancer, I decided to try Cali's crappy 91 and I get consistently 10 more mpg.  It seems to idle best with 91, and runs better overall.  I'd say experiment with different brands at the same octane, and swap it up a bit until you find something you like, then stick with that.

[mjm]

i have a gs500 F 2004 and i wanna know if using the 87 type of gas is good?  the manual says to use it, but im just wondering if there is a better type of gas, like the 89 and such?  sorry if i sound stupid... thank you though.

Octane is simply a measure of resistance to detonation - also called pinging or knock.  So long as the engine is not knocking there is no advantage to higher octane gasoline. If you engine has a knock sensor (and the GS500 does not) then it will retard timing when knock starts - reducing power and eliminating the knock.   GS 500 manuals that call for 91 octane are refering to Research Octane - US gas is the average of Research and Motor Octane ratings - 87 under that system is exactly the same thing as 91 under the research method.

That said, if you have a higher than standard compression ratio and/or an ignition advancer then there might be an advantage to using mid-grade in the GS.  My 2001 has the advancer and runs fine on regular.

For those who think that higer octane is a higher quality product - you are simply wrong.  It is more expensive - but not because its higher quality.

[Roadstergal]

even though my manual (96 gs) suggests 91 octane minimum.

Are you sure it's 91 AKI?  AKI is (RON + MON)/2, and my manual ('00 GS) suggested 87 AKI.  No problems with that (actually, that's what the SV and GS both take, too).  If you have a grade of gas that's high enough octane to prevent knock, more octane won't do you any good.

[duma]

omg, i used to have the post lists listed as OLDEST first, no wonder i iddnt c my post after i posted... i thought they were deleted.  anyways, so ignore what the manual says?  hmmmm my gs is brand new... if using other type of gas other than what the manual says is ok?  thx again

[Ed89]

omg, i used to have the post lists listed as OLDEST first, no wonder i iddnt c my post after i posted... i thought they were deleted.  anyways, so ignore what the manual says?  hmmmm my gs is brand new... if using other type of gas other than what the manual says is ok?  thx again

87, 89, 91 is all fine.  Most people here run on 87 I believe.  I run on 87.  I ran on 91 for a long time, but switched to 87 a few months ago with no visible ill effect (no noticeable difference in mileage per gallon).  I don't think the GS has enough compression to come close to pre-igniting 87 gas.

If you don't feel comfortable with 87, go down slowly: use 89 for a while and see if you notice any ill effect (unlikely), then when you feel comfortable enough, drop to 87.

Cheers,
e.

[tdan553527]

I have an 04, and have ran 87 in it since i bought it in march. 11,000 miles and no problems. I usually average right at 60 MPG.

[scratch]

Srinath uses 91 in stock bikes and 87 in jetted ones.

[Jace009]

I drive a ford escort which they recomend minimum of 91oct...  
It just clicked over 300k miles on the car and 128k on the new engine that I rebuilt a while ago...

On a bike like the GS that has low compression [for bikes] 9.1:1 I think it is. 87 is fine there will be no detonation...if you ride a bike like a ninja that sports 13:1 compression then ya 87 is going to denate all over the place and run like crap.

[Nerobro]

our bikes are carburated.  So our knock detector is between our ears.  Listen to the engine.  If you hear knocking, you should lay off the throttle alittle untill you can put higher octane gas in it.  Lower octane gasoline actually contains more energy than higher octane gasoline.

IIRC lower octane gas is also denser.  So you run a little richer for a given needle/jet setting.  Don't hold me to that yet.  I do need to go doubble check my facts on that.

I tend to use lower octane gas as much as I can.  

Keep in mind.  MPG is defined by your carbs, and your wrist.  Not the fuel you use.  With a fuel injected car changing octane rating can alter MPG becuase the car will change the fuel mixture or injection timing to prevent pinging.  If you have a lot of retardation the car will see lower fuel economy.

[Roadstergal]

No, there isn't more or less energy in higher octane gas.  It's resistance to detonation.  That's all.

Some gas companies put a different additive package in premium vs. mid-and low-grade gas, but the only rule for octane is - if it isn't knocking, you're good.

[coll0412]

I am not sure if lower octane rated fuel has any more energy, I do know that the "activation energy" for octane as well iso-octane(C8-H18) is higher than that of  heptane. The octance rating of heptane is 0 and of 100% ocatane, and iso-octane  is a rating of 100. The nice thing about octane is that this actavation energy or how much "free energy" is in the system has to be greater than that of heptane.

Or in other words the total amount of tempature change that the fuel experiences has to be higher for octane to combust that that of heptane.
So if you are on a hot day(100 degrees F) and you are putting a heavy load on our air cooled twin, it develops hot spots inside the cylinder, any points that have a high surface area to volume, will begin to heat up enough, so that as the piston compress the fuel air mixture, temp rise from the comperssion and  ontop of our devopling hot spot, we get a boom it fires before your 1000K tempature spark is ever used. The problem is that the piston is still moving up, the spark plug fires, and you have two flame waves that collide and you hear a ping. Where they collide  you blow of microscopic peices of the metal, and if it works jsut right the flame fronts collide around the plug and blow little peices of the ceramic.

Now if you can maintain the temp of your engine and do not put a heavy load, a rating of 87 octane works great, but on hot dry days, your engine first can't cool very well since air is a poor conductor of heat(plus it takes longer for the engine to cool when it hot,..ie Newtons Law of Cooling), and the "ocatane" requierment is higher because the air charge temp is higher, higher cylinder temps all lead to a higher total energy of the fuel so basically it is already hot, and doesnt need much farther to heat to self-detonate.

Now if you really wanted a slick way of increasing your ocatne rating is use a water injection system, the water is a great conductor of heat and abosrbs the heat from the fuel charge to prevent detantation.


I am pretty sure this is all right, but any corrections are more than welcome

[duma]

i still dont know what yall mean by "knocking."  sorry, i have very little knowledge in the world of mechanics... im in a process of learning.  so please forgive me for asking a stupid question.

[davipu]

as long as it's not diesel your fine.  save your self the 20 cents a gallon and always buy the cheep stuff.  and my two cents on the subject, if you have a advancer gap the plugs .015 over (it'll run real crappy) and put in a whole bottle of octane boost,  :mrgreen:  you'll really notice it over 9000.  IF YOU DO TRY THIS DON'T BLAME IT ON ME WHEN YOU BLOW UP YOUR MOTOR.  but it is really fun.

[duma]

haha alright, have u tried it? heheh

[GSRider]

I used to run 87, and now with re-worked carbs and shimmed needles, I run 91. 94 sucks ass.

FWIW, I have a good friend who rides a 929, and he puts 87 in the tank, and has absolutely no issues with pre-detonation; in fact he says the bike runs worse on higher octane fuels.

Remember folks, the higher the octane, the hotter (Possibly) your engine will run. And considering we have air-cooled engines, engine temperature is a very important factor, and we must always bear this in mind. (The reason why I shimmed the needles in the first place)

Here is some more info on pre-ignition/detonation, if you care to read it all:

Knock, also called pre-ignition, occurs when the fuel gets too compressed and hot and burns on its own before the spark plug ignites the mixture. It's called pre-ignition because ignition is happening earlier than it should. When you compress a gas, it gets hotter. If you compress fuel-air mixture enough, it gets so hot that the temperature reaches the flash point of the fuel. Pre-ignition is the result. An overheating engine can also contribute to pre-ingition. But either way, pre-ignition has absolutely nothing to do with the fuel burning "inefficiently."

What is high-octane fuel? Basically, it's fuel that has a higher flash point when in a vapor form. It is, in essense, fuel that doesn't want to burn as easily as lower-octane fuel. This is why some people argue that high-octane fuel actually gives slightly less power. IIRC Kevin Cameron once made this argument in his column. I'm not sure how true this is. Surely, any power loss due to knock inhibitors must be miniscule. Less power? Probably. And a carbon fiber gas cap also makes your bike lighter, but it's not a difference anyone is really going to notice.

High performance engines usually have higher compression ratios, which means that pre-ignition is more likely to occur. This is why high-performance engines often require high-octane fuel. Highly modified race cars often have extremely high compression, so it's not uncommon to see race gas with an AKI octane rating of 96 or 97. For this reason people often associate high octane with high performance. Certainly, high octane fuel is often required by high performance engines, but it is not the fuel that gives that high performance. In reality the high performance comes in spite of the fuel.

Sportbikes often have high performance engines, so some of them actually require higher-octane fuel. Check the owners manual and follow the manufacturers recommendation. There is no benefit whatsoever to running a higher octane fuel than what is required, and any peace of mind you may get from it is false. If your owners manual says that your bike should run on 87 octane but it pings on 87 octane, there's something wrong with your engine.

Audix_dude lives in South Africa and it sounds like they use the RON scale, which is what is also used in most of Europe. The USA uses the AKI scale. 91 octane fuel in Europe (and probably South Africa) is about the same as the fuel marked as 87 octane in the USA.

[Eklipse]

I put in Supreme this tank, I don't know if it's like 93 or 95 octane or what, but it's the highest grade you can get at the chevron here

Anyway, it's working good from what I can tell. I have 250 miles on this tank, and I'm usually on reserve by 180. It's not that I've been doing gentle riding this tank either.

I've been riding pretty hard, I actually hit 130mph on this tank (I get out with the sportbike riders a lot on Sundays), usually I have trouble getting  120. Did it in 6th gear.

I'm gonna run till I'm on reserve and see how many miles I get, it can't be too much more. I actually double checked today to make sure I wasn't running on RES or PRIME, it's not.

It doesn't really cost much more per fill, I don't know if the extra mileage is gonna be worth it, but it is more, and that means less fillups for me, which is worth it by itself. It seems to sound and run a little better too.

[ghettorigged]

I just want to say that I love that Roadstergal knows about octane....  :kiss:   :mrgreen: