What Lasts Longer..87 or 93 octane..??

Well..yeah i know it's sound Rainman-ish, but i've been using 93 and i think it gets burnt up faster than 87 regular..

my car gets better mileage with 93...
d15b2 engine

your both clueless. . . and i dont feel like explaining this again, its been done to many times. Keep using 93 octane, it gives NA cars massive HP gains. . .sigh

noone ever said anything about power. my car pretty much wont run on anything less then 89 anyways(advanced timing).

The truth is octane has nothing to do with power production. More octane is useless unless it is being used to reduce any present knock.
If you use a lower octaneyour computer might detect knock and then retard the timing, lowering the power but only a little bit. Jayson you are clueless.

Oh sorry I forgot to answer the actual question.

No the octane value of a fuel has nothing to do with fuel mileage.

I think you missed Jayson's sarcasm.

Unless your car recommends premium fuel, then don't use it. You won't gain power or get better mileage but I think it burns a little cleaner if you care.
My car does RECOMMEND premium fuel, so running it does give me more power and better gas mileage. My car runs on 87, but power is definitely down because it retards the timing. It also burns more fuel as you have to give more throttle to get the same speed.
Bottom line is don't waste your money unless your car needs it.

Sorry if i missed the sarcasm, its just that some people are so stuborn and/or uninformed on fuels that they should't open there mouths/keyboards. My apologies Jayson.

wouldnt a very small power decrease (should almost be ommited) by using higher octane if it isnt needed because higher octane fules tend to have less stored energy? j/w.

that and a lighter wallet. :)

Basically, higher octane is less likely to cause pre ignition. (Thats why higher compression motors recommend higher octane with such fuels as CAM-2) On a lot of new cars, low octane fuels can sometimes pre-ignite causing a backfire, or even a slight 'ping'. This drives the knock sensors crazy and causes the ECU to compensate as well as check engine lights to come on. This is very common in volkswagon engines. (but the lights remain on until you take it to the dealer) Higher octane fuels also burn longer. This results in higher operating temperatures. Now, on any normal car, or even slightly modified car, the following means nothing. But on modified cars this longer burning can increase the scavanging effect in the exhaust. Giving SLIGHT hp increases. No, filling your civic with premo doesn't add on another 5 hp next to your 25HP K&N filter...

http://www.clickondetroit.com/automotive/3473463/detail.html

Higher octane fuels also burn longer. This results in higher operating temperatures. Now, on any normal car, or even slightly modified car, the following means nothing. But on modified cars this longer burning can increase the scavanging effect in the exhaust. Giving SLIGHT hp increases. No, filling your civic with premo doesn't add on another 5 hp next to your 25HP K&N filter...

http://www.clickondetroit.com/automotive/3473463/detail.html
a side from the fact that higher octane fules have less BTU potential, too long of a burn will tourch your exaust vualves. my question was if higher octane isnt needed then wouldnt using it cause a slight power decresse due to their lack of stored energy....

Higher octane fuels do not burn longer. One of the requirements of fuel is a fast controlled burn time. Octane gives the control, but burn time is totally different. Higher octane fuels meant for higher revving engines will have a faster burn rate than high octane fuels meant for slower engines. Think about it, why would you want a fuel to burn slower. If it burns faster, that keeps the flame front on top of the piston longer, reduces negative work by reducing combustion on the exhaust stroke, and gives gives more energy ( more fuel burned) on the combustion stroke.

Octane has nothing to do with...
- the flame velocity.
- how the fuel resists surface ignition (pre-ignition, post-ignition).
- the energy content of the fuel.

Don't know why this should be so hard to understand, it have been up several times.

Octane do only measure how the fuel can resist detonation (pinging, knocking or pinking if you prefer any of those names). It's measured in a variable compression test engine and the fuel is then compared to a reference fuel.

If we compare pump fuel, 93 octane contains more energy than what 87 octane do. 93 octane has also a higher density (due to the higher aromatic content). Laminar flame velocity is equal, same goes for boiling curves.

The ideal otto cycle is a constant volume combustion, in reality the combustion is done at close to constant volume. For a normal engine, say that you ignite the mixture at 15 degrees before top dead center, at 15 degrees after top dead center the flame has reached to the point longest from the point of ignition (the cylinderwalls). So with a duration of 30 degrees the piston almost stand still during combustion.

Detonation doesn't increase the engine temperature but it can effectivly destroy the engine, melt holes though the pistons and so on.

Agreed, all octane means is resistance to ignition.

Higher octane fuels do not burn longer. One of the requirements of fuel is a fast controlled burn time. Octane gives the control, but burn time is totally different. Higher octane fuels meant for higher revving engines will have a faster burn rate than high octane fuels meant for slower engines. Think about it, why would you want a fuel to burn slower. If it burns faster, that keeps the flame front on top of the piston longer, reduces negative work by reducing combustion on the exhaust stroke, and gives gives more energy ( more fuel burned) on the combustion stroke.

I sayed its burns LONGER not slower. Slower would be if I said quicker, longer as opposed to shorter. Now, the flame velocity is not related to the scavanging effect, however heat is. (Heat=Excited/Fast moving molecules) With the fuel burning longer, more heat=more scavenging. Heat is what causes this hence ceramic coated headers, heat wrap. It not only keeps the engine compartment cool, but the exhaust temperatures up.

Also, to whoever mentioned burning exhaust valves, that is true.

What the hell are you measuring with you're longer, slower, fatter, shorter, what ever adjective you choose? Time??????
And heat doesn't create scavenging, velocity and pressure pulses creates a scavenging effect. I don't know what science books you're reading, but you might want to get some new/valid info.

What the hell are you measuring with you're longer, slower, fatter, shorter, what ever adjective you choose? Time??????
And heat doesn't create scavenging, velocity and pressure pulses creates a scavenging effect. I don't know what science books you're reading, but you might want to get some new/valid info.
:werd:
i dont understand what you are saying either; you stated it takes longer to burn, but also say its not a slow burn. ie...analogy: if someone is driving slow, doesnt it take longer to reach their destination?:if the mixture is burning slow doesnt it also take longer to burn the whole mixture? ive always believed that high octane fuel is able to burn fast but stable(as in not detonate); thus creating more pressure via heat/expansion more rapidly; instead of letting some useful energy go out the exhaust.

Exaclty. Why would you want a longer burn?

You doesn't need to have your discussion about how long the burn takes as this isn't affected by the octane rating which ONLY relates to detonation resistance.

The burn duration depends on the fuels laminar flame velocity which for pumpgas is around .35 m/s and a lot of other factors like fuel mixture, turbulence in the cylinder and so on. Typically the flame velocity in the cylinder is somewhere around 20-50 m/s.

Thats what we are trying to tell people.

Octane is only a measurement of resistence to detonation.

That is it and nothing else.

:banghead: can i just get a soild answear? When Speaking of 87 v. 93 octane pump gasoline, if your engine does not require 93octane to run properly, will it see a slight power loss from using 93 octane? ive heard rumors and im j/w if they are true. and for anyone who doesnt understand higher octane just equals resistance to detonate, please dont come telling me you will see a power difference due to flame rate. faster = better. end of story. unless you have a massively long stroke and your fule is being completely burned half way down the stroke and then the heat from the combustion is pushing the piston the rest of hte way.

Assuming the vehicle requires 87, it's very unlikely you would ever notice the difference. The BTU difference is very tiny. The opposite is also true...an engine designed for 93 octane due to boost would make the same power until the boost created knock or ventilated a piston. This applies to fuels that are identical except for the octane rating. A fuel with grossly different BTU ratings AND octane ratings is an apples to oranges comparison. Also, fuel burning past 15 - 20 Deg ATDC is not adding any power to the engine, just consuming fuel. Note: I'm not saying there is NO power change (so please don't start the hair splitting), I'm saying that you would likely never notice it in the real world, which is what counts. There are so many other factors that change engine output it would be hard to nail octane as the culprit at the track.

Thanks, so the myths are mostly lies. and yes i know comparing gasoline to Nitro/ethnyl is like comparing a weed wacker motor to a 572...lol