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 87 vs 93 octane
Ok i know this has been beat to death on what to use. But when i went to go over the checklist and all they said that it is recomended to use premium instead of 87. They said it will get better gas mileage and overall performance is better.
Has anyone actually done tests with this to see if there is any kind of difference? Not based on the book but actual tests.
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Another shot at opening Pandora's box. You're right, this has been beat to death and everyone has their opinion Best bet may be to run a tank of each yourself under similar riding conditions and see if you can see or feel any difference. I've been using 87 since day one and consistently get 30 - 33 mpg. Don't know how to measure performance since this thing accelerates like crazy and short of doing 1/4 mile runs with 87 and 93, I sure couldn't tell by the seat of my pants.
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Active Member
Also be aware there are at least 2 different Octance scales.
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 Originally Posted by zzneonzz
But when i went to go over the checklist and all they said that it is recomended to use premium instead of 87.
Which checklist are you referring to?
Regards,
Mark
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Originally Posted by zzneonzz
Ok i know this has been beat to death on what to use. But when i went to go over the checklist and all they said that it is recomended to use premium instead of 87. They said it will get better gas mileage and overall performance is better.
Has anyone actually done tests with this to see if there is any kind of difference? Not based on the book but actual tests.
Yep, the premium costs too much.  Just kidding around. I haven't in the Spyder, but when I had my 06 Electraglide I did try the 87 compared to the premium and got no difference at all, maybe a little higher mileage using the 87.
I've been told the 87 will make you bike run cooler because it takes less heat to burn the 87 in your bike, but I don't know.
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Originally Posted by sleepman
Yep, the premium costs too much. Just kidding around. I haven't in the Spyder, but when I had my 06 Electraglide I did try the 87 compared to the premium and got no difference at all, maybe a little higher mileage using the 87.
I've been told the 87 will make you bike run cooler because it takes less heat to burn the 87 in your bike, but I don't know.
The higher the octane rating, the slower it is to burn.
.
.
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We started putting 93 octane in a few tanks ago - we now get over 50 miles to the gallon, it only runs at 3 bars on the temp guage, the breaks stopped squealing and the parking break doesn't get stuck anymore. go figure. LOL!!!!!!!!!!!!!!!!!!!!!!!!!
Seriously -we are running 93 octane - I am a dumbass and forgot to reset the tripometer but I do feel it runs stronger - it doesn't cough and burp like it used to.
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Originally Posted by Smylinacha
We started putting 93 octane in a few tanks ago - we now get over 50 miles to the gallon, it only runs at 3 bars on the temp guage, the breaks stopped squealing and the parking break doesn't get stuck anymore. go figure. LOL!!!!!!!!!!!!!!!!!!!!!!!!!
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Originally Posted by sleepman
I've been told the 87 will make you bike run cooler because it takes less heat to burn the 87 in your bike, but I don't know.
Actually, you're a little turned around; the higher octane fuel REQUIRES higher heat to ignite. Therefore, one would use a higher octane fuel for a hotter-running engine, not to make it run cooler. Here's why:
The octane rating of a fuel is a measure of its resistance to autoignite -- before the spark plug fires -- from heat and/or pressure. Autoignition is more commonly called preignition -- that little rattling sound you sometime hear on certain engines under acceleration -- and detonation -- a much more destructive ignition malfunction.
The mixture is SUPPOSED to burn in controlled manner, from one side of the cylinder to the other. Many of the recent power and efficiency advances we enjoy in modern internal combustion engines result directly from clever changes to cylinder design which better control the ignition event. When the mixture ignites properly, the expanding gasses push down on the top of the piston at just the right moment, and for just the right amount of time, to convert gas into horsepower to turn the crankshaft, and subsequently the drive wheel(s).
Preignition occurs when a portion or portions of the fuel/air mixture in a cylinder ignite early, before the piston is in the proper position to accept the push of the expanding gases. This sometimes happens when something inside the cylinder (the piston top, a hot spot on the cylinder wall, etc) is hot enough to cause the mixture to ignite. This early ignition -- or "pre-" ignition -- pushes on the piston top while it's still traveling upward on the compression stroke. The energy of that burning fuel is wasted and the engine is actually working against itself.
Detonation is a much more serious problem. This occurs when the mixture simply explodes -- like a firecracker. When an engine experiences detonation the mixture ignites early and burns violently (compared to a normal ignition event). One of the primary causes of detonation is excessive heat. Spray a mixture of fuel/air into a cylinder where the internal heat is hot enough and it will explode -- all at once. That's detonation, and it's bad.
The max cylinder head temp on a typical four-cylinder Lycoming aircraft engine (according to the manufacturer) is 500 degrees F. Just about ANY fuel you can buy at your local filling station for use in your car will ignite at temps far below that number. Which is why these engines use 100 Low-Lead AvGas. (The "100" is the octane rating; "Low-Lead" is a reference to the reduced amount of lead additive compared to the 130 octane AvGas used in WWII era and later reciprocating [piston] aviation engines.) The higher octane rating (and the lead additive) means the fuel simply WILL NOT ignite in these engines until the spark plug fires. The "Old Wives' Tales" you hear about the extreme volatility of AvGas are bunk; you can throw a lit cigarette in a bucket of AvGas. High-octane fuel needs a hotter spark (more heat) to ignite.
Getting back to your statement above, a "fix" one might consider if excessive engine heat were causing preignition or detonation is higher octane fuel. It won't help your engine run cooler, but it might keep it from destroying itself...
Regards,
Mark
P.S. I don't recommend throwing a lit cigarette in a bucket of AvGas.
P.P.S. I'm not aware of anyone reporting any preignition or detonation problems with their Spyder.
Last edited by SpyderMark; 07-29-2008 at 07:41 AM.
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Originally Posted by SpyderMark
High-octane fuel needs a hotter spark (more heat) to ignite.
Right on target, Mark! Many people don't realize this. Probably not an issue for the Spyder, or many modern vehicles with electronic ignitions, but lots of folks in the past wondered why their cars with standard coil ignitions didn't run like race cars with the highly touted "High Octane" fuel. It's like trying to ignite nitromethane in a 6:1 lawnmower engine.  Good explanation!
-Scotty
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Years ago I used to run 100 Low Lead AV gas in my Mod-VP outboard race boat. If any was spilled when fueling, it would evaporate in a split second...much quicker than any other fuel I ever used.
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Just thought I would revisit this thread with my results. I ran 2 tanks of 87 and 3 of 93. With the 93 it appears to run a little better. It doesn't struggle on a cold start to stay running when driving without 2 bars on the temp. I also seem to be getting better gas milage (probably not enough to warant the extra price) but overall performance seems to be a bit better with the 93.
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I too flipped back and forth from 87 to 91 and have noticed the same effects. Starts just fine in the morning, but when it's time to leave work and the engine is already around 108'...has to get to 2 bars or it sputters and pops if I try to roll before hand. I'm not sure if the puter records last outside temp at about 60' when I shut it off and tries to operate in that same parameter when I leave and it's 108' and needs a few minutes to reset or what.
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 Maybe????
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