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

[solaris=amazing]

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..

[Kven]

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

[-Jayson-]

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

[Kven]

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

[bjdm151]

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.

[bjdm151]

Oh sorry I forgot to answer the actual question.

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

[Igovert500]

I think you missed Jayson's sarcasm.

[SUPERMANG]

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.

[bjdm151]

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.

[CBFryman]

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.

[rubix777]

that and a lighter wallet.

[RandomTask]

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/automo...63/detail.html

[CBFryman]

Originally Posted by RandomTask

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/automo...63/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....

[bjdm151]

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.

[SaabJohan]

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.