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Starting Member
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Last Login: 7/16/2007 10:21:19 AM
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| I just bought a new Suzuki Bandit 1250S. One of the plus factors which helped me decide to buy it was that it takes 87 octane (ie regular) gas. Not bad in these days of rising gas prices, single-hose pumps, and shortages of premium gas. Two Questions: 1. Here in Colorado, our regular pumps are 85 octane, and mid-grade is 87. This I atribute to altitude, but should I stick with the 87 octane, or run regular at 85 octane? Is our 85 octane the same gas as 87 at sea level? 2. A salesman at a local shop told me (authoritatively, as they will do) that I should run super duper premium in the bike and gave me the location of a couple of places that sell 104 octane (@$4.50/gal). He claimed I would get better power, starting, mileage, and the motor would run cooler (I wonder if it would grow me some new hair?). Tom and Ray, the tappet brothers on NPR, say this is BS and I'm wasting my money. What do you think? CP
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Average Member
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Last Login: 11/14/2008 10:08:58 AM
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The salesman is BSing you. Using a higher octane than recommended by the manufacturer will not give you more power, etc. What will give you smooth operation and full use of the power in your engine is keeping your carbs or injectors clean, plugs clean and gapped properly, serviced and timing checked on a regular basis and use a mild (not overly strong) carb or injector cleaner in your gas tank occasionally. (Check with your mechanic or the manufacturer to see what cleaner is recommended). Keep your air cleaner system clean and don't let the filter get real dirty.
What you will notice if you use a lower octane than your engine requires, especially if you have a high compression engine, is an octane "ping", which you can hear when accelerating hard or when the engine is under load. This is not good for your engine and you would be wise to either change gasoline brands or move up to the next higher octane available. Don't use 104 or any other specialized (aviation, racing, etc.) fuel in your bike. That almost twenty point difference you mentioned (87 to 104) is way too much of a difference and your bike will probably run worse because it's not timed properly for real high octane gas.
The old theory that high octane gas makes your vehicle run better comes from oil companies putting in additives in their premium brand. The additives probably cost them about 1 cent a gallon but make drivers think they were doing something good for their engines.
I've never heard of any difference in octane ratings according to elevation. There is a difference in the air and it does affect the air-to-gas ratio in your fuel system, especially on older bikes. Some late model bikes have systems that recognize changes in altitude and adjust accordingly.
Bottom line - follow the manufacturer's recommendations on minimum octane and then use your own common sense - if you get an octane knock move up to the next higher octane for a tankful and see if it goes away.
Now, let me get this right - is it one down, four up?
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Junior Member
Group: Forum Members
Last Login: 11/13/2008 2:08:59 PM
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| On a recent trip across Washington state I encountered regular gas at 85.5 octane rating on the pump. It worked fine. Octane rating is reduced at higher altitude -- apparently the 85.5 produces about the same effect at altitude as 87 octane does at lower altitude. I've seen this before in Colorado and Idaho when riding through. No problems. The lowest octane that works and doesn't produce pinging is the best for your bike. Higher octane is less volatile, hence the predisposition to reduce ping. Less volatility produces poorer cold weather starting. In the past premium grades of gas had more detergent additives to keep the crud from building up on the valves and piston crowns. Federal mandates now require all grades to contain these chemicals -- although premium MIGHT contain more, although I doubt it. All of my recent bikes have used regular, starting with a Gold Wing in 1983, an Intruder, a Bandit 1200, a Burgman scooter, a W650 Kawasaki, and my current Boulevard M50 Suzuki. Even a Royal Enfield 500, but that compression ratio was so low (6.5 to 1) it would probably run on kerosene. Ray Nielsen, in Minneapolis and went for a ride today.
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Junior Member
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Last Login: 11/17/2008 5:01:46 PM
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The man who told you to run the super prem. did not know what the hell he was talking about. The sad fact is he probably thought he was right. After all in America if it cost more it must be better in some way. Not true for gasoline. I retired from a oil refinery after 31 years there. All gas is manufactured the exact same way, using a platinum catalyst. The octane is then raised using alkylate to the desired rating. The additive package is added by the distributor after the gas is delivered to him. As someone else said all grades are now required to have the same amount of the additive. Of course you have to rely on the distributor to add the package, it is not checked by anyone to my knowledge. the package is very expensive. As for as running the 85 oct. in you bike in Colo. it should pose no problem. Modern fuel injected bikes run better at hight alt. and get better fuel mileage also. I have done lots of riding where the regular is 85 oct. with several different bikes and they ran great. By the way, all refineries only make two grades of gas. regular and premium. The distributor then blends them to make the mid grade. Again you will have to rely on him to be honest and blend it at 50% regular 50% premium.
"Life's journey is not arriving at the gate safely in a well perserved body, but rather to skid-in-sideways, totally worn out, shouting...holy *...what a ride!"
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Average Member
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Last Login: 11/14/2008 10:08:58 AM
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So they do reduce the octane at higher elevations. I may have to tell my wife I need to do a research trip on octane content.
SV - what exactly is in the additive package they put in gasoline?
Now, let me get this right - is it one down, four up?
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Starting Member
Group: Forum Members
Last Login: 7/21/2007 6:38:32 PM
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| As stated previously, octane is an anti-knock additive used in gasoline to prevent pre-detonation of the air-fuel mixture in the engine. Many things contribute to why a certain octane rating is recommended like compression ratio, bore diameter, fuel-air ratio, and even spark plugs have some effect (think heat range). High compression engines with small bore diameters can tolerate lower octane ratings vs. large bore diameters with similar compression ratios like big block motors. Knocking occurs when your cylinder temperature & compression are too high for the grade of gas your using. At that point you need to step up one octane rating. If your engine isn't knocking, you may want to try using one rating lower but listen to the engine when it's under load or climbing a hill to see if there's any knocking. I'm at 4500 ft above sea level and have never had any problems using a lower grade octane from the manufacturer's recommendations. The reason being that the air-fuel ratio here is richer than similar settings at sea level. Most bikes have open-loop fuel injection systems which do not read the emissions via an O2 sensor and therefore dump fuel based on a pre-programmed fuel map. This is not the same as automobiles with OBDII fuel injection systems that can modify the fuel-air ratio based on many more variables including altitude. Something important to note about octane: An increase in octane will increase the burn time of the flame. I have heard that running high octane mixtures like AVgas (104 octane) can actually burn a hole through a piston because of the prolonged burn cycle and localized heat at the top of the piston. You may want to check with some mechanics to confirm this. People mistake this extra burn time as "more power" but in reality it is less power since the piston has already moved past the optimum point during crankshaft rotation and the mixture is still burning. Airplanes usually have very long strokes that can take advantage of the longer burn times to increase torque - but how long do airplane engines run before they get rebuilt??? Hope this helps a little - and saves you some money on gas!
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Junior Member
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Last Login: 11/17/2008 5:01:46 PM
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| Rootie, refineries do not have to reduce the octane for high elev. them simply do not have to raise the octane. Higher octanes cost money. The first process is the refinery is the reformer unit. The octane there is controled by the heat of the furnaces. Heat cost money and also expends the catylast at a faster rate. When the reformate leaves the reformer the octane is raised by the addition of alkylate. Alkylate is very expensive. Gasoline going to areas such as Colo. cost the refinery less money to produce. But they do preform as well as higher octane gas at lower elevations. As to the additive package, every major oil co. has its own package but as for as the fuel injection cleaner in the package, it is all the same, under a license to Dupont corp. They have a patent on it. How much is used is up to the individual company. It also is very expensive. In my humble opinion, if you use a national branded gasoline, you will be OK. After all, they all want you to be a repeat customer. When I am traveling on my bike I will use any gas available when I need it. When home in Austin, I use one of the major brands. Hope this helps. l
"Life's journey is not arriving at the gate safely in a well perserved body, but rather to skid-in-sideways, totally worn out, shouting...holy *...what a ride!"
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