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Came across this article on high octane-

The facts on High Octane Gasoline

Do you buy a high octane gasoline for your car because you want to improve its performance? If so, you should note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner’s manual recommends offers absolutely no benefit. It won’t make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner’s manual.

The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars. If it was designed for regular gas, but knocks, often that means you need a tune up.

Unless your engine is knocking, buying higher octane gasoline is a waste of money, too. Premium gas costs 15 to 20 cents per gallon more than regular. That can add up to $100 or more a year in extra costs. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need.

What are octane ratings?

Octane ratings measure a gasoline’s ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane) and premium (usually 92 or 93). The ratings must be posted on bright yellow stickers on each gasoline pump.

How is octane rating determined?

Gasoline is subjected to two testing methods to establish its octane rating: one, called the motor method, runs the gasoline in an engine under load; and a second, the research method, runs the gasoline in a free running engine. The research method gives slightly higher ratings, and the octane number displayed on the pumps is an average of the two methods.

What’s the right octane level for your car?

Check your owner’s manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars, old cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.

How can you tell if you’re using the right octane level?

Listen to your car’s engine. If it doesn’t knock when you use the recommended octane, you’re using the right grade of gasoline. Knock occurs when cylinder pressures are high. It is normal for an engine to ping a little at full throttle because cylinder pressures are very high at full throttle. Engine knock, however, should not be ignored since it can result in serious damage to the engine. High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high.

If your engine runs well and does not knock or ping on low octane gasoline, there is no advantage in switching to higher octane gasoline.

If your engine knocks or pings, it does not necessarily mean something is wrong with the gasoline. It could be a problem with the car's ignition timing or exhaust gas recirculation. On high mileage engines, a carbon build-up in the cylinders can increase cylinder pressures and cause knock.

Will higher octane gasoline clean your engine better?

As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car’s engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

Should you ever switch to a higher octane gasoline?

A few car engines may knock or ping - even if you use the recommended octane. If this happens, try switching to the next higher octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.

Is knocking harmful?

Occasional light knocking or pinging won’t harm your engine, and doesn’t indicate a need for higher octane. But don’t ignore severe knocking. A heavy or persistent knock can lead to engine damage.

Is all "premium" or "regular" gasoline the same?

The octane rating of gasoline marked "premium" or "regular" is not consistent across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium. To make sure you know what you’re buying, check the octane rating on the yellow sticker on the gas pump instead of relying on the name "premium" or "regular."

Does high octane gasoline improve mileage?

In general, if your car is designed to run on 87 octane gasoline, high octane gasoline will not improve mileage. If switching to high octane gasoline does improve mileage, you might find that a tune-up will give you the same improvement on 87 octane gasoline.

Does high octane gasoline achieve quicker starting?

No, it doesn't.

Does high octane gasoline increase power?

If your car is designed to run on 87 octane gasoline, you shouldn't notice any more power on high octane gasoline. Again, if it does make a noticeable difference, you may need a tune-up.

Is high octane gasoline more refined -- is it just a better product?

Additional refining steps are used to increase the octane; however, these additional steps do not make the gasoline any cleaner or better. They just yield a different blend of hydrocarbons that burn more slowly. The additional steps also increase the price.
 

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Exactly what my experience indicates.
 

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Good info to know!!:cheers::bigthumb:
 

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I was watching Nascar earlier, and they dedicated a portion of the preshow to this and agreed with everything you quoted above. I have to say though, if all gas comes from the same refineries and 93 octane doesn't run better, there must be something else going on.
I had a chevy that ran noticeably better on Mobil gas, a Lexus that loved Shell 93, and the FJ I have to say runs awesome on a lot of different types of gas (I still run Shell whenever I can though).
There's a ton of threads on this board and on many other boards discussing this. Maybe it's the way each station is run, who knows. I do know the few times I've put no name brands in my cars, they ran horribly.
 

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So was the FJ engine designed aroune 87 or 91?

I know the one tank of 87 I ran, the FJ ran like sh!t.

87 or 91 is a debate that will never be resolved.
 

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So was the FJ engine designed aroune 87 or 91?

I know the one tank of 87 I ran, the FJ ran like sh!t.

87 or 91 is a debate that will never be resolved.

Your dead on sir!!! I also had the crappy feel on regular.

I'm beginning to get a severe case of Deja moo (the feeling you've heard this bull before), like you said this sort of posting is without end.

Sorry let me correct myself, informative post however I can see this spiraling into another another debate.
 

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If you guys are using anything other than regular you are wasting your money. Slow down, use 87 and you will find you FJ gets the same mpg either with 87 or 93. The same tanker truck fills all the tanks at the station, their is no difference in fuel....
 

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So was the FJ engine designed aroune 87 or 91?

I know the one tank of 87 I ran, the FJ ran like sh!t.

87 or 91 is a debate that will never be resolved.
It was designed to run on regular unleaded. It's the same engine that is in the Tundra regular cab base model, the 4Runner and the Tacoma. In those vehicles the HP an torque measurements were achieved with regular 87 octane fuel.

The FJ had the HP and torque measured utilizing 93 octane fuel, resulting in a 3 hp increase......thus the premium sticker on the door.


Love Ya, Mean it :mecry:
 

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It was designed to run on regular unleaded. It's the same engine that is in the Tundra regular cab base model, the 4Runner and the Tacoma. In those vehicles the HP an torque measurements were achieved with regular 87 octane fuel.

The FJ had the HP and torque measured utilizing 93 octane fuel, resulting in a 3 hp increase......thus the premium sticker on the door.


Love Ya, Mean it :mecry:
Is it the same ECM? Maps and curves in the FJ ECM maybe different? Not saying it is just specuating.
 

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The engine in the FJ has high compression. The timing curve changes with lower octane because of the chances detonation can increase if it isn't changed, hence why most feel a sluggish behavior when using lower octane.

That octane myth makes you think like this, if you pay for Vavoline or Castrol oil would you use even cheaper oil in your mind?

I am sorry, yes, it is technology of the ECU that keeps the engine from detonating itself but the fact of the matter is...

the FJ has a high compression engine period, if you want optimum performance, use the higher grade.

My experiences from using different ratings shows that there is a MPG difference and there is a difference MPG in brands. I always get crappy gas mileage if I buy a certain brand at various locations. I have always got better MPG with Exxon.

Now when i was a member of the GSCA (it's a Buick club) there would be topics such as this one and engineers and those in the field would chime. It was a interesting read but I know this, those with 8.0:1 turbocharged engines would run 87 octane if on a budget but made sure they were not running an agressive chip. Same with the V8s with high compression, they would have to back the timing curve off. There was a difference in performance of the engine due to the octane because you had to sacrifices to prevent detonation.

That clearly shows you that there is a difference with octane with performance engines.
 

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It should be noted that our ecm's need a bit of time to re-map so if you go from premium to regular (especially in states that have 92 or 93 octane premium, Alaska only has 90 octane) it could take a tank or two to allow the ecm to adjust to the octane. It will run a bit crappy at first but as the computer learns to use regular performance will improve to a point just below what you get with premium. Our cars were designed for premium or the manufacturer wouldn't have put it in the manual and on the gas cap. This doesn't mean they can't run regular though. The ability to adjust to regular octane and run ok says a lot about the engine in our FJ's.

I've used regular before, but usually get premium myself. $100 extra a year is nothing in the grander scheme of things and gives me piece of mind.
 

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Our engine's got a pretty high compression ratio and therefore I personally would not recommend lower octane. I'm sure you won't feel any knock from the lower octane but i still will not use it (until gas hit $7 :D) i believe the manual state 91? our engine will not run optimal with 89 or lower. lower octane would run fine on cars from other decades, but not on the FJ imo..
 

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It wasn't retracted. A Toyota Bulletin went out that said that it's o.k. to run RUL with no worries. The FJ still makes it's rated HP/TQ/MPG with PUL.

DEWFPO
 
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