Gasoline - Octane.. what's the deal

[ironforge]

Just was at the pump this morning... put premium in my car.. took $40 to fill it up..

just wondering how much difference there is between regular, plus, premium.. etc..

what exactly is the octane rating? I have a little bit of knowledge on the subject.. but clarification is appreciative

(P+M)/2 method is typically what is used I think.. anyone can explain the formula?

[Lemon[H]ead]

its probably to do with how environment friendly it is...

oh hang on you're in the states..."environment friendly" isn't in your vocab... j/k

[Cruez]

There is a little difference. Depends on what the car was designed for.

If it says "unleaded fuel only" you will be better off putting 87 octane in it...

If it says "premium fuel only" you can probably bet that it will be pinging away due to detonation....or not run very well on 87 octane..

Some cars may say "premium recommended" that means there is a noticable difference in performance, but it will run fine on lower grade fuel and have better performance with premium...(not many cars say this)

These are more or less generalizations.....if you are putting premium in a car not designed for it.....you are probably wasting your money....unless you have modded your car to take advantage of it...

[ironforge]

Even if the performance gains might not be there...
would higher octane gas be cleaner for your engine?

I have been putting premium in my truck just because it is new.. heh.. got to feed the v8 something eh?

[vass0922]

Agreed with cruez, everything I've heard says that if you're car is not designed for premium (and it will tell you!) dont' bother with premium gases..

Also from what I've heard no it doesnt help clean fuel injectors either

[Cruez]

Originally posted by ironforge
Even if the performance gains might not be there...
would higher octane gas be cleaner for your engine?

I have been putting premium in my truck just because it is new.. heh.. got to feed the v8 something eh?

I doubt it... I had a Datsun Z car that the engine had over 365,000 miles on it...... very little buildup on the pistons....I ran plain jane 87 in it.....with an occasional FI cleaner.

[desmocat]

Almost all grades of gasoline have a detergent additive in them.I think the EPA/Gov't more or less requires or mandates that.(in the US)
Also, a lot of engines have "knock" sensors in them, and will retard the spark timing to try and compensate for preignition "knock", and I guess you could try running regular, mid grade, and super to see what the lowest octane you can get away with running before you notice it pinging or the performance degrading. I have a 97 dodge ram 1500 with a 5.9 L andfor about the last 3 years, I have always ran 87 octane in it, even when pulling my boat and never had any problems. Mid grade and super were ran in it to the tune of about 3 months straight each, and I couldn't tell any difference in the mileage or the performance, so I went back to regular unleaded and been ther ever since. 147,000 miles on it too.

[Brainchild]

regular is 83 plus is 86 and super is 90 but some companies carry 93. At least that's what it is around here. Mostly the higher the octane, the less the ping the engine will produce under load. In high performance engines, this means you can run more advance in the timing, and gain significant performance boost. I'm not so sure that with newer engines, designed for the lower octane fuels it will make that much difference, performance wise,I could be wrong.

[ironforge]

here it is 87, 89, and 91

can it damage your engine if you run higher octane than designed for? or only if you run LESS than it was designed for?

[HfdWolfPack]

Everyone has there own theory on this, but from what I gather, if your car says 87........run 87.

and if it isn't running well on said 87, something is wrong other than the octane level.

I was a big "higher must be better" but when the difference in price was .20 a gallon , I looked into it.
My car runs just as well on 87 as it does on 89 and I never bothered trying 90+ with my new car.


As far as being "cleaner".....I heard if the car is supposed to be run on 87, it is actually the opposite.