higher octane gas to compensate for ethanol

[USSEnterprise]

Hello,

Would it do anything for fuel economy and/or performance to use a higher octane fuel, considering that there is less bang in ethanol blended fuel? (can't get e0 in NJ)

 

[SJC4Runner]

It wont have the effect your looking for. Ethanol doesn't have as much energy when it burns. It actually has a relatively high octane rating, which is more a description of how fuel burns.

Ethanol - Wikipedia, the free encyclopedia

The reason performance cars use higher octane is to enhance when and how the fuel burns. The additional power comes from more fuel and pressure (from high compression or forced injection), rather than the fuel itself.

My 4 runner is setup to run with 87 octane. When functioning correctly, it will achieve it's best power and fuel economy on 87 octane gas. This being at sea level, should you be at higher elevation you can use less octane to get the same results, which is why in higher elevation states you see 85 octane. If you add a supercharger your changing the pressures the engine is operation under and higher octane gas is required.

 

[98OzarksRunner]

Higher octane (premium) doesn't do anything to enhance performance or economy. Engines that have high compression, superchargers/turbochargers, or aggressive tunes (more ignition timing) NEED higher octane to run safely, but the octane level has nothing to do with power. In fact, since higher octane fuel burns more slowly it probably decreases performance very slightly. The 'higher octane more power and better mileage' myth is just a misunderstanding of how engines and fuel work.

Having said that, ethanol-free premium might increase fuel economy slightly since ethanol does contain less energy thus provide slightly less mileage. You will probably notice less than 1 MPG difference, but pay 20 cents a gallon more for it, so it's a net loss.

Edit: Some ECM (engine computers) use knock sensors to control timing and if less knock is detected allow more ignition timing to produce more power and better mileage. That is not a function of the octane, but the ECM compensating for lower or higher octane, so it is possible you might see some improvement in both. But I seriously doubt our 4Runner ECMs are that smart!

 

[pauls4runner]

The car I had before I got my 4runner was an 04 Chevy Aveo (1.6 etecII 4cyl) designed to run on 87 oct. when I would run 93 octane, it had a little more pep and mpg went up by 1 or 2

 

[badattitude]

I can get, and use 87 octane 100% gas. In my 3.4 4runner. My unscientific data suggests I get about 1 more mile more per gallon on 100% gas. I pay about 12 cents more per gallon for 100% gas here.

I look at like this...I'm paying 3.5% more money for 100% gas ($.12/$3.40)

I recieve 5.5 % better fuel milage using 100% gas. (1mpg/18mpg)

Is my math bad?

Not to mention, I assume straight gas is better for my engine and sensors?

Boo ethenol, now what I really want is a bio-diesel 4runner. And of course, a place to buy bio-diesel. lol

 

[badattitude]

Also, I concur...there is no reason to buy higher octane gas unless you have a pre-ignition ping. That won't happen until you are supercharged.

Buy 87 octane for max HP in the 3.4 liter.

 

[Dagobah]

The higher the octane, the cleaner it burns. This means fewer deposits and carbon buildup; A cleaner engine. My dad has a 1990 F150, and he only uses 87 octane. Every once in a while he'll fill her up with higher octane to try and burn away some early stage carbon buildup. This was at the suggestion of our very knowledgeable mechanic.

 

[IanB]

The higher the octane, the cleaner it burns. This means fewer deposits and carbon buildup; A cleaner engine. My dad has a 1990 F150, and he only uses 87 octane. Every once in a while he'll fill her up with higher octane to try and burn away some early stage carbon buildup. This was at the suggestion of our very knowledgeable mechanic.

Octane rating has nothing to do with "cleaner burning", but higher grade fuels often come packaged with additives such as detergents that will clean deposits in the engine. This has nothing to do with the octane rating though, octane rating refers to the detonation resistance of the fuel only. If you buy premium at your grocery store or other bargain source, odds are it won't have the same additives you'd find in premium at a major gas station.

 

[LittleCaesar]

I choose between 89 and 91 each time I fill up. Around town there seems to be no difference in MPGs. For highway driving, the 91 does yield better MPGs. Non ethanol gas is better than both ethanol based ratings IMHO, whatever grade you can ind it in.