Does premium unleaded burn hotter than regular

Status
Not open for further replies.
Originally Posted By: daves66nova
The numbers are just ratings for the level of resistance to detonation,it is not an indicator of "performance"

Quoted for truth. Octane is associated with performance because high performance engines have designs that require higher octane. Turbocharging, supercharging, high compression are all reasons that an engine has more performance, they are also reasons they need high octane so they don't have pre-ignition. Pre-ignition can rattle an engine apart and/or burn holes in places they shouldnt be.
 
Last edited by a moderator:
By and large,NO.
ANY substance added to the gas that helps prevent, or delays preignition with give the Gasoline a higher octane rating.
For may years a type of Lead compound was used, Methanol and Ethanol will also serve to raise the octane rating. But they will not cause the fuel to burn hotter.
 
Nope, not hotter, faster, slower, or any of the things that our local mower repair man keeps telling my co-workers.

It is merely more resistant to self igniting in the presence of pressure, temperature, and hot spots.

It used to (often) have a lower energy content, but modern refining has made high density high octane fuels.
 
Originally Posted By: RTBandit
Just curious - Does 91 octane gas create a hotter explosion than 87 octane? All input is appreciated.


It's not an explosion, it's a burn.
Or it should be!
 
Octane rating does not relate to the energy content of the fuel. It doesn't burn any hotter.
 
Some cars had warnings years ago on running high octane fuels as they were set to use regular. The reason given was burning exhaust valves. This was not due to higher temps but to a slightly longer burn time that produced a hotter exhaust gas that caused the exhaust valve to run hotter. My wife's Saturn has a warning like this in the owner's manual and I think Buick may have had it as well.
 
Is this on a bet? Having a Molotov Cocktail? If you want more energy out of a cylinder burn you have to add MORE fuel and MORE air. Or Nitrous (air) and more fuel. Not enough air will make the burn too hot.
 
I don't know if it burns hotter but it burns slower. That's why you need to adjust the timing on older cars to not ping on lower octane fuels.
 
Originally Posted By: Bluestream
It burns slower, so my guess is it would be cooler


This is a mistake many people think - just because it is less prone to pre-ignite, through additives, does NOT mean it burns slower.

Once ignited, Premium burns at basically the same rate as Regular.
 
Last edited:
So running 93 octane in an engine that calls for 87 will not lead to increased carbon build up compared to running 87 all the time?
 
The btu content is the same.

It is a "flash", not an explosion. A nice little envelope of expanding flame front.
 
Originally Posted By: Jax_RX8
Originally Posted By: Bluestream
It burns slower, so my guess is it would be cooler


This is a mistake many people think - just because it is less prone to pre-ignite, through additives, does NOT mean it burns slower.

Once ignited, Premium burns at basically the same rate as Regular.


It's not a mistake. Higher octane fuel does burn slower. The slower burn prevents knocking under high cylinder pressures.
 
Originally Posted By: mikered30
So running 93 octane in an engine that calls for 87 will not lead to increased carbon build up compared to running 87 all the time?


It will not. The only thing it will lead to with a car designed for 87 is a flatter wallet.
 
You definitely don`t want to run regular in a car that`s designed to run premium. My last 4 cars were spec`d to run premium as is my present car. I tried regular in my old 300ZX turbo one time and it would barely make it up a hill if you put your foot in it. It would ping so bad that the engine would barely run. I topped it off with premium and the pinging was immediately gone.
 
Premium fuel burns slower than Reg; everyone knows that. That's why it can give more power in an engine that has been designed for premium, as it ignites it will expand and apply even force as the piston moves down. Reg may be burned up before the piston is all the way in it's downstroke and a "ping" or "knock" is the result. Any difference in the temp of the burn would be insignificant

I have owned 2 cars that called for Premium, and I always ran regular or mid-grade. On my Olds, and my Jag, the knock sensor will retard the timing if any pinging starts...
 
Last edited:
Status
Not open for further replies.
Back
Top