4-Bangers and octane

Just in case people didn't actually go read the Federal Trade Commission link I provided above... here is the contents of that page.

The Low-Down on High Octane Gasoline

Are you tempted to buy a high octane gasoline for your car because you want to improve its performance? If so, take 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.
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.

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 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.

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 highest 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."

For More Information

If you're concerned about the accuracy of an octane label - or if you don't see a yellow octane sticker on a gasoline pump, write: Consumer Response Center, Federal Trade Commission, Washington, DC 20580.
The FTC works to prevent fraudulent, deceptive and unfair business practices in the marketplace and to provide information to help consumers spot, stop and avoid them. To file a complaint or get free information on consumer issues, visit ftc.gov or call toll-free, 1-877-FTC-HELP (1-877-382-4357); TTY: 1-866-653-4261. Watch a video, How to File a Complaint, at ftc.gov/video to learn more. The FTC enters consumer complaints into the Consumer Sentinel Network, a secure online database and investigative tool used by hundreds of civil and criminal law enforcement agencies in the U.S. and abroad.

 

I could not see any difference so went back to 87. Drove 352 miles before the fuel light came on. I filled up at 17.1 gallons so I guess I had 4 in reserve. 06 4x4 5 speed, 113000 and it purrs.

 

Mine runs great on 85, which is the lowest grade in the mountain states.

Don't need as much octane since the cylinder pressure is effectively lower at this altitude, it's not just about compression ratio. No knocking so no need for anything higher.

 

when filling my 5lug 31" tires with 91 i noticed less diesel sound at low rpms lugging it. I cant say anything for performace though. just less luggin sounds from the engine, and in my opinion with bigger tires and no rear gear swap i am running higher octane as insurance against knock, at least in this summer heat. If you are towing i would suggest the same.

I can say without the timing curve adjusted for this octane I would expect no increase in performance or MPG.

BUT if your pcm is reducing timing due to knock retard from increased load(bigger tires stock rear gears, hauling, trailering, heatsoaked and A/C lol), you may see a benefit from running a higher octane.

I do agree under normal conditions 87 octane should be more than enough for this engine.

 

Well I'm one of the few that have to use 93 octane. My engine Knock when lunching from first gear and gave 17.5 MPG I switch to 93 the Knock is over and know I have from 18 to 19 MPG with an average of 18.5 MPG.

I did the math and with 1 MPG difference I can pay up to 0.05 cents more per litter and still brake even with 87 Octane that is up to 0.19 cents per gallon and if you get bigger difference the more you can pay without really overpaying for it.

But just for not having that Knock sound I'm willing to over pay a litter bit more and have my engine on the save side. Good for you who don't knock with 87 octane you are bless.

 

i run 91 oc

 

You should fill your tires with air instead of 91

 

But he has a super long range using tires as extra tanks........the increase in inertia will be a killer to acceleration.

 

Oh that Canadian humor

Isn't there a bullshit section u guys can troll

 

its probably already been said but the 2tr's have one map and its tuned for 87. if you can get a piggyback and get someone to tune for a different octane fuel then you will get performance gains from 91 because the timing and such would be altered for optimal performance, otherwise your just wasting money.

 

These octane topics kill me.. the engine will make the most power and be the most efficient with whatever is engineered to be ran! This has been proven over and over again, its a NUMBER not a performance increase. Everyone thinks that because one gas is more expensive than the other its better! WRONG. I have dynoed street bikes to prove this, my gsxr 600 calls for 87 octance, i dynoed it with 87, then dynoed again wiht 93 and lost almost 6 horsepower on top!

 

The only differance I have seen is from ethanol containing and straight gas. Less MPG with the ethanol.

 

Your all correct but what happens when you increase engine load and start seeing spark advance pulled because knock sensors are seeing knock

 

No knock sensor on I4.

 

Don't know about all this octane rating stuff.

What I do know though, come winter time running a tank of 87 is like pouring water down the drain. I had to switch up to premium to get any kind of sembelance of MPGs, and even then it still really sucked.

Winter, higher/longer idle, cold air, stop lights, short trips, school zones/buses/stops out the ass. Yeah...I hate it.

 

Now that I run premium, I see a HUGE performance difference! In fact, my truck hits 248rwhp on a dynojet, and the butt dyno is loving it too...

Well, the premium, and the supercharger. The supercharger probably helped some too...

 

87 runs just fine in my 2.7, I tried higher octanes w/ no gains; just wish ethanol-free fuel was readily available here...

 

The two times I have tried premium I got around 1mpg less than the previous tank.

 

Yes, there is. Proof, right from the shop manual...

 

I stand corrected.