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Does it matter if I run 87 octane or 92 octane gas

H

hsp

Member
"Just curious if running the S

"Just curious if running the Super Unleaded 92 octane gas makes a difference? I normally just put regular unleaded 87 octane gas.

I did run 6 gallons this past weekend on 92 and notice I had some knocking noise.

thanks,

JR"
 
"You don't say what motor

"You don't say what motor you have but 87 octane should work fine. Outboards love octane, the higher the better, so if you are hearing a knocking noise, you should check that out."
 
"Knocking may mean preignition

"Knocking may mean preignition. Preignition may mean a hole in your piston or beating the top ring land so bad it'll spray ring bits all over the cylinder.

In particular, many V-4s have small top ring lands that are susceptible to disintegration.

Stick with the 87."
 
outboards are meant to run on

outboards are meant to run on 87 period
the higher the octance the hotter the burn
when u get running psi around 170-185 is when u need 92
 
"Justintime,

I am with you.

"Justintime,

I am with you. 87 works fine. I talked with one of my friends that owns a gas station. The says they don't even know what grade gas they get. Sometimes it say 91 and there is really only 87 in the pump.

Larry"
 
"There have been laws regulati

"There have been laws regulating how gasoline has been classified and dispensed at the pump since the 1920s. Tell your friend that if the oil company or distributor he buys from is putting 87 octane in his 91 tanks then not only is it against federal law, it is fraud, pure and simple."
 
"so true ken, but it happens.

"so true ken, but it happens. mistakes are made, and it is not always fraid. Humans are not perfect. At lease that is what I tell my self all the time. LOL.

Larry"
 
"The octane rating of gasoline

"The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

I agree that 87 is fine in outboards. However, the octane rating doesn't really have anything to do with the temp of the burn. The above paragraph is from "How stuff works" and it explains octane ratings and what they mean. A motor should not knock on 92 octane but run without a knock on 87, assuming that there is no damage in the engine.

Here is another explanation from www.theserviceadvisor.com

WHAT IS OCTANE RATING?

Octane, by definition, is the resistance to burn or detonation. The higher the rating, the slower the burn when ignited during the compression burn cycle of the piston. The higher octane allows for better control of burning for high compression engines. So we want to match the correct octane rating of the gasoline to the engine design to ensure complete burning of the gasoline by the engine for maximum fuel economy and clean emissions"
 
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