I decided to splurge a little and give the GS some 91 octane last week. what a mistake..she started to sputter revving thru 2nd and 3rd afterwards but after she got hot it was less frequent. After a half tank I filled her up with some 87 octane to compensate. She ran much better but still not as smooth as before. Waiting for the tank to get down to half again before I fill her up with some 87 or 89.
The question is should I filled her up with the usual 89 or the more expensive 87? Also why is that 87 octane is more expensive then 89 octane?
where are you located that regular (87) is more expensive than plus (89)? My bike always get the regular and haven't had any problems yet with it.
our unleaded is 95, in england.
Iowa..price 91>87>89..odd huh?
using 89, 91, or 93 doesn't make your bike faster or give you more HP. It's just a waste of money and can make your engine knock. Please stick to 87 unleaded. Here is a wiki explanation.
It's a common misconception higher octane = more power. WRONG!
http://en.wikipedia.org/wiki/Octane_rating#Effects_of_octane_rating
Quote from: tussey on September 11, 2009, 04:49:07 PM
using 89, 91, or 93 doesn't make your bike faster or give you more HP. It's just a waste of money and can make your engine knock. Please stick to 87 unleaded. Here is a wiki explanation.
It's a common misconception higher octane = more power. WRONG!
http://en.wikipedia.org/wiki/Octane_rating#Effects_of_octane_rating
A-FU#!@%-MEN
I'm tired of trying to convince people of exactly that.
Higher octane doesn't mean more power. The main, if not only reason we have the "good stuff" if for high compression engines. If there is a reason, I'd like to know so chime in. :D
Quote from: karl on September 11, 2009, 02:30:29 PM
our unleaded is 95, in england.
RON - we Yanks use AKI.
Quote from: tussey on September 11, 2009, 04:49:07 PM
using 89, 91, or 93 doesn't make your bike faster or give you more HP.
True, but I don't buy that it screws up yer average 87 engine to use higher. When I'm done with a race weekend, I dump the excess 91 into my SV, which takes 87, and it runs just the same as it does on 87. I've done that on a few stock only-needs-87 bikes, and they all run just the same. No better, no worse. Your symptoms sound just like when I had old gas (87) that had accumulated water in my old GS.
Quote from: tussey on September 11, 2009, 04:49:07 PM
using 89, 91, or 93 doesn't make your bike faster or give you more HP. It's just a waste of money and can make your engine knock. Please stick to 87 unleaded. Here is a wiki explanation.
It's a common misconception higher octane = more power. WRONG!
http://en.wikipedia.org/wiki/Octane_rating#Effects_of_octane_rating
It's the LOW octane that causes engine knock, not the high octane. And only in higher compression engines. And on a bike that's around 9:1 and up.
Michael
Low octane fuel will allow a high compression to "diesel" or pre-ignite and, of course "knock" big time. A low compression engine will typically run best of the lower octane. Using higher octane in a low compression engine can lead to imcomplete combuston and excessive carbon build-up in the combustion chambers and upon the backs of the valve faces. As the carbon builds-up it can make hot spots that can also pre-ignite the air fuel charge and thus cause knock. Further, carbon build-up can be rather remarkable if allowed to continue and the combustion chambers effectively become smaller as the choke-off with all that crusty stuff in there -- thus compression rises and pre-ignition can occur form that.
I've seen some bikes that were VERY sensitive to higher octane fuel, especially 2 cycle bikes where the fluffy carbon very quickly fouled the plugs. There is actually a tad more energy in lower ocatane fuels.
Regarding regular being more expensive than plus or premium; I hope they at least use a condom.
prs
This is the first time I've ever heard of 87 octane costing more than higher octane fuels. Every gas pump I've ever visited in my life had 87 octane as the cheapest. This does not count the time when octane ratings were not posted on the pumps, as I predate that legislation, but regular is what the GS runs well on, so more expensive, higher octane fuels are not needed and can cause hard starting in cold weather and absolutely does cause higher emission levels of unburned hydrocarbons. I know they sell 85 octane in some places, but I've never been there. I'm curious to hear from GS 500 owners if it runs well on 85 octane.
The only reason I can think of why regular gas is more expensive than mid-grade where you live is perhaps very few people where you live are buying high octane gas so you have a situation where there is a glut of premium and a relative scarcity of regular. There are only two tanks underground, three if they have diesel. The pumps mix regular and premium to deliver mid-grades. Sunoco is famous for this as they've been doing it the longest as far as I know.
Hang on, I just thought of a reason why regular might be more expensive. It may have a lot of ethanol in it in Iowa. Ethanol is more expensive today than gasoline, so a high ethanol content would drive-up the price. If that's the case, you need to send angry letters to your congressmen!
This is the second time I've heard of crappy regular fuel in Iowa. I have an XS 750 triple so I also visit the Yamaha triples website. A guy named Ray also complained about the same thing, and the XS 750 only has 8.5 to 1 compression, so it doesn't need any more octane than the GS 500. Ray can't run regular in his XS in Iowa, but he should be able to.
It's not a secret that with your GS you should treat it like a lawnmower where gas is concerned. Regular is best, but using 89 shouldn't upset it. 2 octane points isn't a big deal, so I'm thinking you have water or some other contaminant in the gas. Either that or since you live in corn country there may be too much ethanol in regular Iowa gas and your bike doesn't like it. I put premium in my bike once because they were out of regular and I was in the middle of nowhere. The bike ran the same, but the weather was warm so I didn't run into any potential cold weather starting problem.