difference between 87 and 89 octane gas?
Thread Starter
Senior Member
Joined: May 2002
Posts: 412
Likes: 0
From: Philly,PA
difference between 87 and 89 octane gas?
I've been using 87 in my civic ex for a while. But then when I bought another civic(used), I decided to use 89. I was wondering is there a difference between the two for sohc engine? cuz it's 7more cents for 89 
Great Taste, Less Filling
Joined: Sep 2002
Posts: 67
Likes: 0
the lower the octane, the lower the fuel's flash point, which is the pressure and or temperature it takes to make the fuel ignite... so 87 octane gas ignites easier than 89 octane, and much easier than 93 or 94 octane. Once you add performane mods to your car, you almost always need to use at least 93 octane gas, to avoid detonation (the gas exploding in the cyllander before the spark plug fires, causing major stress on the internal components of the motor). For a stock SOHC, just look in the owner's manual to see what octane Honda reccomends for the car, and run that for the most part... although you may want to splurge occasionally for 93 or 94 octane gas, as it usually has more detergents and cleaning agents in it, to aid in removing carbon build-up inside of the engine. Since I dont know what the reccomendation from honda is, I would personally tell you to go with atleast 89 octane... and if possible, ask around to find out what gas stations are reliable... in my area, the good ones are Exxon and Chevron... because less reliable stations have a tendency to water down thier gasoline, which is bad for performance.
I know this all seems like quite a pain to go through, just for gasoline, but remember that choosing the right gas and the right oil are 2 of the biggest factors to maintain a well running, long living engine.
I know this all seems like quite a pain to go through, just for gasoline, but remember that choosing the right gas and the right oil are 2 of the biggest factors to maintain a well running, long living engine.
Le Grand Illusion
Joined: Oct 2002
Posts: 1,180
Likes: 0
From: Damascus, MD
turbo/nos/supercharger will requre 93+ octane.
anything less - I/H/E - will be just fine at 87.
detergent levels are universal for 87/89/93... it's a federal law that only a certain % of gasoline can be cleaning agents, to regulate prices and quality. One of my best friends was a gas station manager in Charleston, SC... he wondered the same thing with his '95 Eclipse GS-T, and looked it up. So don't worry about that much...
But brancato1 is absolutely right about quality of the station being important... watered down gas can really mess up an engine. As a rule, generally avoid the independant "C&C's Gas and Go" type places. They buy the gas from the bigger guys, but have much more freedom to mess with the quality after it arrives than the big companies - who have stockholders, the feds, etc. to answer to. Thus, Amoco and Exxon have lots to lose, and Tucker's All-Nite Gas Depot doesn't.
anything less - I/H/E - will be just fine at 87.
detergent levels are universal for 87/89/93... it's a federal law that only a certain % of gasoline can be cleaning agents, to regulate prices and quality. One of my best friends was a gas station manager in Charleston, SC... he wondered the same thing with his '95 Eclipse GS-T, and looked it up. So don't worry about that much...
But brancato1 is absolutely right about quality of the station being important... watered down gas can really mess up an engine. As a rule, generally avoid the independant "C&C's Gas and Go" type places. They buy the gas from the bigger guys, but have much more freedom to mess with the quality after it arrives than the big companies - who have stockholders, the feds, etc. to answer to. Thus, Amoco and Exxon have lots to lose, and Tucker's All-Nite Gas Depot doesn't.
wooooo woooooooooo
Joined: Mar 2002
Posts: 3,134
Likes: 0
From: Twin Cities
I've always gotten better mileage with my sol with higher octane. Basically come down to how long do I want to go between fills. It ends up being the same cost per mile... So, I say, why not use 92 and not have to stop as often??? But, like was stated, some little stations have crappy gas...
Great Taste, Less Filling
Joined: Sep 2002
Posts: 67
Likes: 0
Check out www.howstuffworks.com... here is what they had posted for octane:
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.
The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.
The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.
It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.
During WWI, it was discovered that you can add a chemical called tetraethyl lead to gasoline and significantly improve its octane rating. Cheaper grades of gasoline could be made usable by adding this chemical. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:
Lead clogs a catalytic converter and renders it inoperable within minutes.
The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).
When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline, and octane ratings of 115 are commonly used in super-high-performance piston airplane engines (jet engines burn kerosene, by the way).
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.
The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.
The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.
It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.
During WWI, it was discovered that you can add a chemical called tetraethyl lead to gasoline and significantly improve its octane rating. Cheaper grades of gasoline could be made usable by adding this chemical. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:
Lead clogs a catalytic converter and renders it inoperable within minutes.
The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).
When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline, and octane ratings of 115 are commonly used in super-high-performance piston airplane engines (jet engines burn kerosene, by the way).
I'm not planning to use 93 for my sohc. There's no mod on it. I just need fuel economy 
Le Grand Illusion
Joined: Oct 2002
Posts: 1,180
Likes: 0
From: Damascus, MD
91 octane? That's impossible to find where I am - you'd have to 50-50 with 89 and 93. I'm not convinced it's the best gas for the SOHC, no matter what Honda says.. I've haven't seen any difference at all between 87 and 89, so far.