Higher octane?
 

What are the pros/cons of using higher octane in a non-tuned engine? I thought I'd give it a minor whack and put 20 gallons of 87 in my tank on tuesday and 4.3-something gallons of 89 in it. so far i dont feel any change.

should it help/hurt gas mileage/HP/idle/anything? if nothing, im going to ave my 4 pennies/gallon and go back to all 24 gallons of 87.

unless your timing is advanced its not going to help anything. your not gunna go put 93 in your truck and all the sudden run 10's

So nothing? just trying to understand, but why do some manufacturers design engines to run off higher octane (much more expensive in the long run) when you can save thousands and make a 87-octane engine? my uncles nissan maxima runs off premium and i almost shat myself when i saw his fill-up bill.

• 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:

You can file a complaint with the FTC by contacting the Consumer Response Center by phone: toll-free 1-877-FTC-HELP (382-4357); TDD: 202-326-2502; by mail: Consumer Response Center, Federal Trade Commission, 600 Pennsylvania Ave, NW, Washington, DC 20580; or through the Internet, using the online complaint form. Although the Commission cannot resolve individual problems for consumers, it can act against a company if it sees a pattern of possible law violations. The FTC publishes free brochures on many consumer issues. For a complete list of publications, write for Best Sellers, Consumer Response Center, Federal Trade Commission, 600 Pennsylvania Ave, NW, Washington, DC 20580; or call toll-free 1-877-FTC-HELP (382-4357), TDD 202-326-2502.
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Cool. Although you could've left out the bottom part, I dont need that :lol:

In some vehicles with a knock sensor, higher octane gas will SLIGHTLY improve the performance and mileage.


Putting 4 gallons of 89 on top of 20 gallons of 87 won't do squat. You now have a tank of 87.4 octane - whoopie doo. If you want to play, run it down till the light comes on and fill it to the top with 93, and try to find some that doesn't have ethanol added. See what your magic gauge reads for mileage and horsepower and draw your own conclusions. Regardless of what some people may say here, you will not hurt a thing by doing it. I've done it and noticed a slight difference, but it's not worth the extra 20 cents a gallon to me.

Next time I have some extra cash...runs some numbers....$3.50 lying around, I'll fill her up with some 92 and see how it runs. I primarily get my gas from Murphys (Wal-Mart) and down here in Fla, I shouldn't expect any ethanol added to it, should I?

In this day an age, I would think so...

i dont remember seeing that much of it down south. if your up north its a different story. that **** is everywhere

Murphy's is 10% ethanol nationwide if I'm not mistaken.

Be Warned
 

Back when I used to drive my '99 Chevy Metro, I would fill up with mid-grade gas because the engine would make less noise going up a certain hill. I figured it was just better for the engine. WRONG.

Six years later I was plagued with problems. My engine light was coming on all the time with EGR codes. I had to continually remove my EGR valve, clean out the soot, blow out the valve, and reinstall. It took me a LONG time to correct that problem, and I can't say what kind of gunk it may have left on the intake or exhaust valves.

I realise that a 4.2 liter Ford engine is vastly different than the 993cc Suzuki engine that powered my Metro, but if you've ever watched Mythbusters, you'll understand that small scale tests often replicate themselves in the larger scale.

The octane rating of fuel represents nothing but it's RESISTANCE to burning. The higher the octane, the harder it is to ignite the fuel/air mixture. Some engines (i.e. Corvette, Viper, Lambo) require a high octane fuel because the temperature and pressures inside those engines would cause regular gas to ignite LONG before the spark plug fired, resulting in engine damage.

Putting higher than recommended octane gasoline in your truck will NOT give you any kind of performance/MPG increase, but it WILL harm your engine. The heat of the combustion chamber plus the spark will not be enough to completely burn the gas/air mixture. The result will be carbon deposits and soot. This soot will build up where ever it can, and will cause you problems in the long run.