What fuel octane are you running?

[KEITH KRAUSE]

I have a '79 GS1000E with a Wiseco 1085 kit, V&H pipe and K&N pods. In California I always ran 91 octane since the bike was new and to be honest, I never knew if it was necessary. All my friends said to run 91 or "you'll get pinging". I still run 91 here in Utah. I've never tried any octane that's lower.
I'm going to have to strip and clean my carbs for the second time in two years because the gas here (up to 10% ethanol) is gumming up my carbs. I know part of the problem is I don't ride the bike often enough and the garage gets over 100 degrees in the hot months. That's not going to change.
I want to run the "pure" gas to stop gumming up the carbs but it's only available in 88 octane here.
The factory manual says to "use only unleaded gas of at least 85~95 octane (R+M/2 method) or 89 octane or higher rated by the "Research method". I generally buy Chevron, 76, or Mobil. I don't know what method they use for their octane ratings.
Does anyone know how to find out what methods are used for various suppliers? What octane are you running and what modifications have you done? I appreciate any help/experience you can share.

[Steve]

As far as I know, all US-branded gasolines use the (R+M/2) method. The 87 octane that is available in most places as "Regular" certainly meets Suzuki's minimum requirement.

Your engine has been built-up a bit, which might require a bit more octane, possibly requiring 89 octane. The requirement for additional octane goes down with an increase in elevation. I think the elevation where you are is quite similar to where you were, so that would not change much. In higher places, like Colorado, "Regular" grade gas at the pump might be 85 or 86.

But, to answer your question: all of the bikes in my garage (bone-stock engines) work just fine on "Regular" 87 octane fuel.

.

[gsrick]

I use non-ethanol all the time if it's available and ours down here is 89 octain, but I run 87 many times and have had no detonation, but then my bikes are stock compression.

[Nessism]

After fighting with gummed up carbs on my (now departed) 1000S I started using Sta-Bil and never a problem since. I used the marine version but the regular version should be fine too.

[Steve]

For general use during the riding season, I seldom (almost never) use any additives, but for winter storage, I'll use Sta-Bil. Have not tried the marine version that everybody seems to like. I just use about double the dose on the 'regular' stuff and it seems to work quite well. I think the normal dose is about one ounce per gallon. I will dump an 8-ounce bottle into my5+ gallon tank (partially-filled), then ride to the gas station. The super-strong dose gets through the carbs on the way, then I will fill the tank the rest of the way and go "around the block" to make sure ALL circuits in the carbs get their dose of treated fuel. The size of the "block" will depend on the air temperature, it might range from about a mile to well over 25 miles. When I get home, I will change the oil and filter, then park the bike until it's nice enough weather to venture out again.

.

[Burque73]

86 octane here, no issues with the 850G or any other bike I've had. All stock G model GS's, a DL1000, KLR650, and and this little KLX400 have all done fine. My rides start at a mile above sea level and can range from 3k feet up to 11k feet or so.

[Nessism]

With the Marine Sta-Bil it only takes 1/2 oz for 5 gallons so the bottle lasts a long time. I use it for pretty much every fill because there are gaps of time between rides sometimes.

[gsrick]

I had an instructor at MMI that said we don't have much of a problem with pre-detonation in Fl, because our humidity and the moisture in the air is a natural octain booster or pre-detonation eliminator. He told us that he was the guy that went through Ducati's race engines in prep for the Daytona races and also said you can pee in your tank to raise the octain. You can take that however you want, but he didn't mean that you should do it. I wonder what they are putting in that expensive high octain fuel they offer at the pumps?

[steve murdoch]

The only way to get ethanol-free gas in my area is 91 octane Shell V-Power.
I use it almost exclusively because the bikes are not ridden regularly.
Stock engines.

[limeex2]

If the compression has been raised you should be running higher octane. If you dont run it often, run non-ethanol only. My Triumph calls for and runs fine on 87 octane. If it sits for more than 4 weeks it wont start till I drain the carbs. Follow the directions for Sta-Bil with very short term storage and use non-ethanol fuel. Winter storage? Use same gas, little more sta-bil(or equivalent) and DRAIN the carbs. All problems are eliminated when drained, not run dry, DRAINED. Its 4 screws to turn. I've had zero issues in 20+ years of winter storage of multiple bikes when drained.

[jabcb]

I use 91-octane ethanol-free Marathon gas in all my vintage bikes. Use Stabil at the end of the riding season.
Having a small collection, I view it as a cost & time savings. They charge a good bit more for the ethanol free but I don’t have to fuss with all of those carbs.

[Nessism]

There is no ethanol free fuel in my area and it seems that anytime beyond 3 months in storage w/o Sta-Bil is a gamble.

Regarding octane rating, I use the lowest that my bike will tolerate without knocking and find that most GS's get along well with 87 octane regular. For a big bore equipped bike 87 may not be enough though. Regardless, Sta-Bil works great and is cheap. Unless pure gasoline fuel is readily available and cheap in your area I don't see the point when Sta-Bil can be added easily enough.

[bccap]

Chevron in my town offers ethanol free gas at 94 octane. That is what I use as the bike isn't turning a wheel too often these days. Should go out and get some Sta-bil as well as at the end of the month it will be stored til March........

[Gorminrider]

In Canada anyways, Shell 91 and Chevron 94 are methanol-free. But personally, Petrocan is fine with me. Ethanol has never been a problem. In fact, when it first came out, Iused to especially goto Husky stations for my Rambler....

My Suzukis all run fine on anything BUT seeing as my Honda says it wants "91" I trust them...and seeing the specs are remarkably similar to the Suzukis, in compression ratios and rpm, I take it that an 89 or 91 is not a bad idea forSuzuki too, especially on the highway or mountains. 94 IMO verges on a real waste of $ versus my insecurities so I don't buy it very often .

After all, these higher octane gasolines are not used all that much by other vehicles are they? Old gas? other gas from the plumbing? I wonder what I am actually getting if the pumps aren't frequented by other bikes and hot-rods. something I mean to check out...

as to "85-95 per the (R+M)/2 method " the (R+M)/2 is also known as the AKI and is posted on the pumps in the USA and Canada by law.

Being that AKI (AntiKnockIndex) is a kind of average of the RON and MON ,I have it noted that "As the formula indicates, gasolines with the same AKI can have different RONs and MONS... This may explain why a vehicle knocks while running on certain brands of gasoline or even between fill-ups of the same brand."

....or 89 or higher per Research Method"
well, I copied this from somewhere. Trivia perhaps....
RON is determined in a single cylinder variable compression ratio engine that operates at 600 RPM with a 125’F inlet air temperature at standard barometric pressure. Spark advance is fixed at 13′ BTDC. In a real world engine, RON is necessary to satisfy part throttle knock problems. A good quality racing gasoline has a RON in the range of I IO to II 5. A high quality racing gasoline can have a RON in excess of 120, which is the top of the octane scale. The difference in the spread of RON is not very important to racing engines.

The procedures and hardware for the RON test were originally developed in 1931. The hardware was revised in 1948 with procedural changes made until the late 1960’s...."

and
"MON is more important to racing engines. "...It is always lower than RON..." "MON is determined in a single cylinder engine similar to the RON engine with a few changes that make operating conditions more severe and therefore the octane numbers are lower. The MON engine runs at 900 RPM with a 300’F mixture temperature. Spark advance varies with compression ratio. In a real world engine, MON is necessary to satisfy octane demands at wide open throttle. This is a very important number for racing engines since they spend a high percentage of their lives under high speed and high load conditions. Racing engines cannot afford to be short on octane quality, since detonation or pre-ignition will quickly reduce a racing engine to junk...."

[scratch]

If a bike doesnt get run in a couple of weeks I start getting nightmares about the ethenol doing evil. Sta-Bil helps me sleep well... but, if it goes on a few weeks the carbs are coming off, getting a quick cleaning and going in a plastic tub with a lid and the bike will be surrounded by garlic & a ring of mousetraps. I actually love cleaning carburetors but, not if they have to be cleaned because I was lazy and let 'em sit till the gas got shmutzy, that just makes me feel guilty.

My GS bikes (none are high compression, all are 8v, no 16v) seem very forgiving about gas if my ignition, valves and carbs are dialed...

That said, have had other bikes that were picky about gas so, I still aproach it on a case by case basis.