Higher octane vs lower octane gas

[kunia]

I've been running 87oct gas for close to 8 years in my 4runners - never had an issue. Two weeks ago I started a little 91oct experiment - I'm now on my 2nd tank of 91 gas.
Now, call me stupid, or maybe it's just my imagination, but the 4runner (V6 4x4) runs smoother - it feels like there's more power at lower RMPs - and and my fuel economy is better: was 12.5L/100, now it's 11.7L/100 (mixed driving)

 

[parboy]

higher octane burns hotter, ignites faster, and burns cleaner due to heat and is meant for high compression high performance engines. It will make more power. In older engines you will notice a bit of difference if you have spark knock or valve flutter. I don't think you are going to get jaw dropping results running it in your 4runner. I remember when we were younger I had a older 72 olds cutlass with a 350SB and you could go and get this fuel called CAM2. It was 110 Octane and we ran it in our Late Model Stock car. It was racing fuel. Clean and purple. We would mix it with 93 to get it to about 103-105 and it would make that Monte Carlo run like a Jack Russel after a rabbit.. it was a good idea at the time but was the ultimate end of the engine in the long run but 350 engines were a dime a dozen and a swap was a 6 hr deal.

 

[MikeInNH]

It will make more power.

It will make more power IF AND ONLY IF the engine is designed for higher octane.

If will NOT give you one bit of performance increase in the 4runner (since it is NOT designed to run on 91 octane).

Back in the 70's it wasn't uncommon to have very high compression ratio engines. My 67 Malibu SS was 11:1. I rebuilt a couple of 327's putting domed pistons in to get 12:1 compression ratio. 102 Octane was required for those engines.

Using a higher octane then what the engine was designed for will yield no increase in performance or increase in gas mileage. There's not a mechanical engineer in the auto industry who'll disagree with that statement.

As for higher octane burning cleaner....Actually just the opposite if you use it on a engine it wasn't designed for. Some of the higher-octane gas won't get burned when using it in a engine that doesn't require it. This can have some negative effects...like premature catalytic converter failure.

Which Gasoline Should You Buy - Gasoline Chemistry

 

[crackiswack]

higher octane burns hotter, ignites faster, and burns cleaner due to heat and is meant for high compression high performance engines. It will make more power. In older engines you will notice a bit of difference if you have spark knock or valve flutter. I don't think you are going to get jaw dropping results running it in your 4runner. I remember when we were younger I had a older 72 olds cutlass with a 350SB and you could go and get this fuel called CAM2. It was 110 Octane and we ran it in our Late Model Stock car. It was racing fuel. Clean and purple. We would mix it with 93 to get it to about 103-105 and it would make that Monte Carlo run like a Jack Russel after a rabbit.. it was a good idea at the time but was the ultimate end of the engine in the long run but 350 engines were a dime a dozen and a swap was a 6 hr deal.

um no. higher octane burns slower, at roughly the same temperature or lower, and has a lower energy content by volume in almost all cases, especially when ethanol is the main source of the increased octane rating. Race fuel is not a good comparison because it usually isn't sourced from the same refining system and usually has a higher energy content even with the higher octane rating.

 

[DC runner]

Yea. It isn't a linear curve and you defiantly reach a threshold where there is no further gain.

The reason is, the combustion cycle is built for X. X being the octane rating of any engine. Modern cars have variable timing control and can re**** the timing a wee bit to compensate for different grades of fuel. This was discussed, in detail, above. What this means is, if your truck is meant for 89 and you put 87 in it, the car will re**** the timing just a bit to compensate for the different point of combustion.

It will rob you of a a "hair" of power. So little that you will never notice it. It is a mathematical gain/loss.

If, say, you put 93 in a truck designed for 89, you will have NO GAIN. What is unfortunate is we don't teach people this. We don't need to. EFI and ECU's make the need to worry gone.


The Low-Down on High Octane Gasoline

 

[parboy]

like premature catalytic converter failure.

Dang I hate it when that happens :lmao: Thanks for the correction. I ment to say it burns cleaner in Higher compression engines

 

[MikeInNH]

Dang I hate it when that happens

I knew it after I write it...that it might be construed that way.

I ment to say it burns cleaner in Higher compression engines

Agree 100%.....

For engines that "Require" high octane (like high compression engines)..then it's DUMB NOT to use it.

 

[MikeInNH]

If, say, you put 93 in a truck designed for 89, you will have NO GAIN. What is unfortunate is we don't teach people this. We don't need to. EFI and ECU's make the need to worry gone.

It's the gas companies with their "false" advertising that have people convinced to use high-test gas no matter what. If it's on TV....people think it's true...There's a show on the "SyFy" channel that have many "idiots' convinced there really are ghosts.

 

[crackiswack]

For engines that "Require" high octane (like high compression engines)..then it's DUMB NOT to use it.

In most modern engines, it doesn't matter, the performance/mileage hit is small. The ECU will pull timing to prevent knock as discussed above. To get the most out an engine, then yes run premium if the manual says it is required

 

[MikeInNH]

In most modern engines, it doesn't matter, the performance/mileage hit is small. The ECU will pull timing to prevent knock as discussed above. To get the most out an engine, then yes run premium if the manual says it is required

Agree 100%....The ONLY problem that might occur (but it's very rare)...is that the knock sensor may be malfunctioning and if it does...and you ping under hard acceleration...it could DESTROY an engine..but since it's so rare it's not worth worrying about.