Now, the user manual written by your car’s manufacturer is no longer the expert on your car if you have modified the equipment on your car. Your manufacturer does not know what you did to your car, and thus your manual is no longer appropriate to follow. You are in uncharted territory.

If you have modified your car, the responsibility is yours alone, and your tuner’s, to chart the needs of the car, according to a test lab equipped with a dynamometer at a minimum, and possibly auxiliary knock sensors and most certainly an ECU datalogger which can read the knock feedback correction activity within the engine computer while the car is evaluated on the test bed.

So, heck yes, the dynamometer and the datalogger and the knock sensor will demonstrate that your specially prepared car needs or does not need more octane — typically it DOES require high octane on a performance-modified car. Test your car in a lab. Listen to your car. Read the numbers. Do what the numbers tell you to do. If you don’t understand the numbers then you have no business touching your car’s equipment. If you understand what I am saying then you don’t even need my advice.

Otherwise you have no business doing anything with a car’s equipment.

If you do not change the car’s equipment, your manufacturer’s manual is THE authoritative source.

Many of the earlier comments in this thread are very accurate. Can you guess which ones? Otherwise, don’t plan to keep your car for a long time, sell it while you can, because its engine and probably the other parts will be a pile of crap after you are done with it. Happens all the time. Not that everybody cares what they drive. Some people are just happy as pigs in crap.

To add to that, I buy my gas at a wholesale club, so I pay the normal 87 price for 93, which brings my cost to 10 cents per mile.

I’m going to stay with the 93. Especially because I have a few performance parts on my car.

-Nate
Livonia, NY

Drain your tank so that you are running on fumes. Have your wife, girlfriend or significant other fill your tank with either 87, 91, or Jack Daniels for that matter. Make sure they don’t tell you which octane they bought. Repeat the process several times by changing the octane and journal your impression of the results. The drug companies refer to this as eliminating the placebo effect. Your answer will be very clear.

1. The reason you have only had to use 87 octane gas is because modern cars have lower compression ratios and computers with anti-knock sensors. Today’s cars are designed to run on low octane gas. Not only low octane but lead free gas which requires hardened valve seats and in the case of higher performance cars aluminum heads to reduce cylinder temps so that the crap gas will work. – Guess who is paying for all this technology so we can use unleaded low octane fuel? That’s right consumers, and if you think that performance would not be better with leaded higher octane fuel think again, but the design of the car would be different than the crap we drive today.

2. Older cars require higher octane due to a lack of computers/knock sensors and higher compression ratios. Repeat they require it…unless you lower the compression ratio by swapping heads, gaskets, changing the stroke, piston, and adding hardened valve seats. Higher octane premium is not a “myth” for these vehicles it is required unless you modify the motor.

3. Newer cars generally require no more than the 91 or 93 that you see at the premium pump. This is useful for turbocharged, supercharged, and higher compression ratio cars and trucks. Read your owners manual it will set you straight.

4. If you change the boost levels of a turbocharged or supercharged car or add nitrious to the mix you are increasing cylinder pressures (i.e. compression ratio), and you will need higher octane gas. Ricers that are buying this gas may be modified using one or more of these methods. In some cases the best pump gas won’t work, then you need “racing” gas which is now 100 or better. Sadly this gas is barely better than what used in the family station wagon in the 60’s and 70’s. Engine wear was less prevelant with the old gas because the lead that was in our gas lubricated the valve guides and reduced seat temps and prevented valve wear. TEL (tetra ethyl lead) is the best anti-knock compound bottom line. It is still used in AV Gas and Racing Gas. TEL will destroy your emissions system./catalytic converter. Sodium based repacements for TEL exsist but they don’t work as well as TEL.

5. We could go to Methanol (octane 112 or better) and make tons orf horsepower and burn clean and efficient . Methanol requires 2x amount of fuel for each gallon of gas to but only costs a buck a gallon. So equivalently cheaper too but then the car companies and Government would have to find another way to rip people off.

6. Your motor uses the octane that it was designed to use. If you “over” octane a motor there is no damage done the motor will hum along fine but will not derive any extra power from the fuel. If you under octane a motor you can count on having to rebuild the motor long before it should be required and perhaps destroy the motor if it’s a high performance application.

Don’t argue or make comments about something you know nothing about. I read the crap most if you wrote and wanted to puke.

There is no “myth: premium fuel is a neccesity in some cases and the consumer is paying for the EPA regs through higher fuel prices and all the crap technology that they throw on our cars to burn the no lead low octane fuel. If you had ever driven a real high performance car or race car then you would know when you really need a higher octane fuel, nothing worse than stomping the pedal only to hear the engine destroying sounds of a piston slapping the cylinder wall “ping”. Maybe you guys should discuss the benefits of nitromethane next that will be a real hoot.

Higher octane will not burn higher unless it contains more ethanol. the more ethanol in your gasoline the hotter it burns, and less HP BTW, reguardless of the “octane” rating of ethanol, the required Air fuel mixture is 5 times that of gasonline. HIgher octane should burn cooler.

Please use the fuel recomended for your car, and leave that decision to the people designing cars, because honestly, lay-people don’t know anything about whats going on inside their car.

On any car, the higher octane you run, the more timing advance you can run, so as long as your cars computer can command it, and your fuel can support it, you can get more timing + and more HP. (boosted, high compression cars especialy)

to the mini owner, use the highest octane you can get… 93 is good.

personaly, i use 94, although im trying to find some 100 unleaded local… and yes, my car needs it. I also get 34-40 MPG highway.