Gasoline Octane Rating

[Samuel]

i read this in the recent issue of Men's Health Magazine and it was in a Q&A column.

Q: Is Premium gasoline really any better than regular?

A: It all depends on what kind of vehicle you're pulling up to the pump, and what the manufacturer recommends to power it. In general, fuel is measured with octane ratings: 87 (regular), 89 (mid-grade), 93 (premium). Since premium fuel is higher quality, you may think it would burn faster and is therefore more of a rip-off than lower-grade gasoline. However, the higher octane rating means the fuel actually has a greater resistance to igniting. Most performance vehicles require a higher-octane fuel because burning low-octane go-juice would cause performance-killing pre-detonation, known as pinging. And, over time, it would wreak expensive havoc--as would using high octane in a normal engine. Burning high-octane fuel in a lower-octane application will also cause damage to your emissions system because the hard-to-burn gasoline won't ignite completely. Worst of all, that'll make your ride smell like a hog farm at low tide.

Nate Pritchett is president of shockermotorsports.com and technical advisor on SpeedTV's Pinks





ok so my question is, does this guy know exactly what he's talking about?

and regarding my 4runner, will it be harmful to the engine if i use 91 octane gasoline?

and i know you will all tell me that you feel no difference when using different octanes but that's just my personal preference and feeling the difference between octanes is something i am not concerned with right now.

 

[Casper]

Actually he does...the higher the Compression Ratio of the engine (taking out forced induction setups) the better you run on higher octane gas as you create more cylinder head temps by higher compression. Running too low can also lead to detonation which is the next step after pre ignition.

Running too high can cause poor gas mileage as well...as he stated, your engine is unable to take advantage of the higher octane.

 

[jeober]

High octane rated gas will burn just fine in your vehicle. If it didn't then you would turn on a MIL (mis-fire detection).

Look at this another way: If high octane gas generated higher emission in a specifc engine then the EPA would have mandated a fix such as a nozzle size exclusion.

 

[jrs2]

Running higher octane gas than your engine requires won't have any negative effect, except on your wallet. Won't have any positive effect either.

Some people use high octane gas even though they don't need to, they think because it costs more it must be better.

Better off spending more to buy quality gas rather than getting higher octane Rotten gas, but that's a whole other discussion.

 

[Samuel]

Running higher octane gas than your engine requires won't have any negative effect, except on your wallet. Won't have any positive effect either.

Some people use high octane gas even though they don't need to, they think because it costs more it must be better.

Better off spending more to buy quality gas rather than getting higher octane Rotten gas, but that's a whole other discussion.

what gas do you prefer? chevron? mobil?

what's considered good quality?

 

[jrs2]

what gas do you prefer? chevron? mobil?

what's considered good quality?

I've been getting Chevron mostly lately, 'cause it's 'quality' and there's a Chevron station close to me. Have no idea if Chevron, Mobil, Shell or any of the 'name' brands are really any different from each other. Or for that matter, if the 'name' brands are really any better than the no-name brands, like Rotten Robbie, World, Ultramar or what ever else you may have in your area. Supposedly the name brands have better additives. I figure for a few cents a gallon more, go with the known good stuff.

A topic like this could probably turn into an almost religious debate.

 

[Camprunner]

The only time I find a need to run 91 or 93 is when I tow my camper (aprox 4,500 lbs). I just feal under load and working the mtr I don't want to take the chance of any knock. Other than that I run 87 and I have no problems.

06 V-6 runner sport.

 

[Jeff Kleb]

Many, if not most, vehicles built during the last ten years or so will have a "knock sensor" inside the engine management system. It will temporarily retard your ignition timing if any pre-ignition (knocking/pinging) is detected. While it might help to save your engine a bit of wear, bear in mind that the altered timing will end up making your engine burn slightly more fuel.

In a nutshell, use whatever octane fuel your vehicle requires - mostly found by reading the owner's guide. A slight ping every now and then under "full throttle" is nothing to get excited about, but your car should not sound like a Powerstroke diesel engine when accelerating to merge with freeway traffic.
:bash:

My 4Runner runs just fine on 87, although I have topped off with premium during long trips just to see if it made a difference. It did not, either in performance or fuel economy. (But that is a strictly unsceintific observation.)

 

[tomhaney1]

Many, if not most, vehicles built during the last ten years or so will have a "knock sensor" inside the engine management system. It will temporarily retard your ignition timing if any pre-ignition (knocking/pinging) is detected. While it might help to save your engine a bit of wear, bear in mind that the altered timing will end up making your engine burn slightly more fuel.

In a nutshell, use whatever octane fuel your vehicle requires - mostly found by reading the owner's guide. A slight ping every now and then under "full throttle" is nothing to get excited about, but your car should not sound like a Powerstroke diesel engine when accelerating to merge with freeway traffic.
:bash:

My 4Runner runs just fine on 87, although I have topped off with premium during long trips just to see if it made a difference. It did not, either in performance or fuel economy. (But that is a strictly unsceintific observation.)

The newer Runners were actually designed and tested using 91 octane fuel. That is what they recommend as well and that is what I use. It will adjust to the lower octane petrol so no harm should be done but I don't want to chance it. I would check Consumer Reports as they acually did a gasoline comparison and from what I remember (please don't quote me on this) Shell was the best pick for its V-Power additive and fuel clarity...

 

[Light_Mania]

Aside from octane, there are differences between brands of gasoline. Check out this site:
http://www.toptiergas.com/
Initially, only Chevron and Quiktrip gasoline were qualifed for this designation.

 

[davefisher]

Just a question, the 4th gen Runners I believe are like this, someone quote me if I'm wrong.

the V6 is higher comp maybe 10.5 : 1 and requires the premium fuel. The V8, running 9.5 : 1 in my manual... recommends premium but only requires 87.

Thoughts? 4th gen V8-ers... what do you run??

 

[Baba Booey]

See what the "engineers, scientists and federal government" say about this issue in the sticky post located above (Premium vs. Regular Fuel).

I run 87 octane in my V6.

 

[Light_Mania]

Because of the high compression ratio, the V6 (and probably the V8) will run a little bit more efficiently and develop a little bit more power on gasoline of a higher octane than 87. Whether or not it is enough to offset the 10 or 20 cents/gallon premium over 87 octane is not so easy to answer.

With fuel prices now over 3$ per gallon, and the increment for 91 octane over 87 octane still only 20 cents/gallon, the slightly greater efficiency might be cost effective. But I think it would be very hard to discover the answer outside of a highly controlled test.

 

[Jeff Kleb]

Just a random thought, but is there a chance that any economy gained by using higher octane fuel could be offset by driving faster? Maybe there is a subconscious thought process that your car/truck "runs better" on premium - thus enabling your lead foot to be a bit heavier.

This is like putting a customized dual-exhaust system on a V8 car of the 1970s. The exhaust system is more efficient, has less back pressure and lets the engine breathe better and produce more horsepower.......but is offset by the "awesome sound" of the engine and the driver will often get on it because it makes such beautiful noise; thus using more gasoline.
:bash:

I have tried using premium or mid-grade from time to time in my 4Runner, but did not really notice a difference in miles per gallon or vehicle performance. Then again, a 4Runner is not a Corvette or Ferrari.

 

[RonMAIDEN]

I run 85 in mine but if I have to go over our mountain passes on a longer road trip I'll use 87. I also seem to get better mileage with the lower octane.

 

[Light_Mania]

The octane/fuel economy equation is further complicated because the component added to premium fuels to boost the octane usually has a lower energy density than the base fuel, therefore requiring a greater volume of higher octane fuel to generate the same heat as 87 octane.

 

[tomhaney1]

Just a random thought, but is there a chance that any economy gained by using higher octane fuel could be offset by driving faster? Maybe there is a subconscious thought process that your car/truck "runs better" on premium - thus enabling your lead foot to be a bit heavier.

This is like putting a customized dual-exhaust system on a V8 car of the 1970s. The exhaust system is more efficient, has less back pressure and lets the engine breathe better and produce more horsepower.......but is offset by the "awesome sound" of the engine and the driver will often get on it because it makes such beautiful noise; thus using more gasoline.
:bash:

I have tried using premium or mid-grade from time to time in my 4Runner, but did not really notice a difference in miles per gallon or vehicle performance. Then again, a 4Runner is not a Corvette or Ferrari.

That's just the point- Try using 85 or 87 octane fuel in a Porsche or other performance vehicle, you WILL know the difference!! I think of it this way, your body can run ok eating McDonalds relatively frequently but fresh foods, fruits and vegetable allow it to perform at its optimum level...Same thing with vehicles, the best yields the best results...