Why our cars need 87 octane gas

[Justin Kirkham]

Speedy-v6-camaro, that is a falsehood. I am sorry. 87 octane fuel does not have more energy in it than 93 octane does. To be honest, no one knows what fuel is best in our cars, with stock tune. To do that, someone would have to run each fuel type in a controlled experiment, and do some math on the dyno results.

Here is a GREAT site to explain these things: Octane Essentials.

-Justin

[ July 21, 2004, 08:19 PM: Message edited by: Justin Kirkham ]

[speedy-v6-camaro]

From
http://www.bajajusa.com/Who%20Needs%...ane%20Fuel.htm

All gasoline, regardless of its’ octane rating, have pretty much the same amount of energy per gallon. What!!! "Sacrilege" you say? Well, actually, some higher-octane fuels have a few LESS percent energy per gallon…so as not to argue over this small point, for the sake of this discussion we will all agree that the automotive gasoline that you buy at the pump, regardless of octane rating, has the same amount of potential energy.

Sometimes fuels do have less energy.

[98Camaro3.8]

Although the energy content is about the same, the lower octane fuel will burn faster, resulting in higher combustion chamber pressures, and will therfore make more power.

Originally posted by Justin Kirkham:
To be honest, no one knows what fuel is best in our cars, with stock tune.

I find it funny that people still refuse to accept that our engines are designed for 87. Higher octane is a waste of money. If your car won't run right on 87, then your engine has a problem.

[speedy-v6-camaro]

Our computers are tuned for 87 octane...you can tune the computer to take advantage of 93 octane.

[dafirebird]

With all that said, what about so-called fuel injector cleaner? Is that actually useful, or is that a marketing ploy, too? And, if it is good stuff, what is the best type for our cars?

I've been using it for years, (The super concentrated stuff). About 1 bottle every 1-2 months. Just to keep things clean, so to speak. Do they have me where they want me????????

Oh, and btw, I use 87 oct. for the most part. Use 93 occasionally, and it SEEMS as though 93 has a little more "kick" to it. And it is to my understanding that cars equipped w/OBDII systems will automatically adjust timing & all that jazz......I think.....

[MustangEater8251]

I use 87 cuz its cheap [img]smile.gif[/img]

Octane side note...

I have heard that the computer will respond to a slight knock by retarding the timing and correcting it, and that in fact by running higher octane it will allow the timing to advance slightly since there is a lack of timing...

anyone know anything about this? Makes sense on paper but hey... so does an eram supercharger ;)

[camaroincal]

Well where's Magnus...we need his input. ;) He's the guru when it comes to this stuff

[john rocco]

"With all that said, what about so-called fuel injector cleaner? Is that actually useful, or is that a marketing ploy, too? And, if it is good stuff, what is the best type for our cars?

I've been using it for years, (The super concentrated stuff). About 1 bottle every 1-2 months. Just to keep things clean, so to speak. Do they have me where they want me????????"

i am curious about this too. i know that when i got back from korea in september i had my injectors cleaned in my 97 and it made a WORLD OF DIFFERENCE. i use 89 in the 97 and there seems to be a noticable difference, especially when my wife sneaks 87 in. and btw. on nawc pt. mugu i pay 2.13 for 89, thats in cali

[mjparme]

Well on the interstate I get an extra 2-3 mpg with 91 octane than I do with 87. In the city I notice no difference in mileage. This was with the stock tune.

Now, I have a 91 octane pcm tune from Westers Garage so I have to run 91.

[Fredless]

I've been running 87 since I bought my 99 back in January.

No problems, decent gas mileage for how I drive it and I ran a 15.647@87.42, with just a lid. Factory everything, I hadn't changed anything tune up wise at that point either.

I tried running 89 and 93 but I saw no increase in power or MPG.

[Brian_D]

"Although the energy content is about the same, the lower octane fuel will burn faster, resulting in higher combustion chamber pressures, and will therfore make more power."

Huh? A given volume of gas combusting at ANY speed slower than that of the time allowed for compression will create the same force.

Just becuase it burns faster doesn't mean it creates more power.

I don't disagree that the engines are tuned to run on 87 octane, but this explanation has no relevancy.

[98Camaro3.8]

Originally posted by Brian_D:
"Although the energy content is about the same, the lower octane fuel will burn faster, resulting in higher combustion chamber pressures, and will therfore make more power."

Huh? A given volume of gas combusting at ANY speed slower than that of the time allowed for compression will create the same force.

Just becuase it burns faster doesn't mean it creates more power.

I don't disagree that the engines are tuned to run on 87 octane, but this explanation has no relevancy.

The piston is on it's way down, so the combustion chamber volume is not constant. If the charge burns slower, the piston will be on it's way down the cylinder, which increases the volume and lowers the pressure. If the charge burned real fast, then it creates it's force in a smaller volume, which causes a higher pressure.

[3.4orNothing]

thanx for that info


the only fuel you get in aruba is 95 octane ,,,so you have tolive with it or run a bike

[saved1]

Fuel injector cleaning fluids are a waste of your money. There are already additives in the gas.

[nikon]

oh my god, this topic has been discussed to death....please just drop it....nobody cares anymore....