So does a change in gasoline matter after all?

[Turbo V6 Camaro]

every cr knocks ever hook aout tap up to you car? every car wil knock at some point and when it does the PCM retard the timing to stop it, loseing power, the less knok it picks up he more the computer advances the timing [img]smile.gif[/img]

[mjparme]

I don't notice any performance difference between 87 and 91 but I have quantified that my interstate gas mileage on long trips is about 2 mpg more with 91 than 87.

I am unsure why this happens. This goes against what I have read about higher octane fuels and what I would expect. Our engines do not have high enough compression to gain anything from the 91. 87 should be just fine. The higher octane rating simply means it is harder to ignite. This is needed for high compression engines as the more you compress a gas the hotter it gets so the fuel air mixture with low octane gas can get hot enough to spontaneously combust in a high compression engine.

[JusFlyinBy]

Originally posted by viper04af:
the less knok it picks up he more the computer advances the timing [img]smile.gif[/img]

It says right in that article that the knock sensor will only retard the timing due to knock, but not advance the timing...

Maybe a stupid question, but, do you lose power when the car retards the timing so it is firing at the right time?

[Turbo V6 Camaro]

yes you loose power when the timing is reatared,

thats right but the pcm looks for maximium HP at wide open trottle, (well gm's deff of max power anyway)

thats way guys with turbo or super charger have to retard the timing on pump gas. really there wasting power, now use race gas, you dont have to retard the timing = more power

less knock less retard more power, constanly adjust the timing, i read somewere a FWD car with the L67 pick up 11 HP and 14 RWT (i think those are the numbers if not vary close) bye chaning to a Lt1 knock sensor!!!

[JusFlyinBy]

Ah, now im starting to get it... So it is pretty likely that my car with 107 kmi is pre-detonating on 87? But the knock sensor is just correcting this so I don't notice, which in turn is causing me to lose power? Anyone else want to chime in here?

[Lon]

i dont notice any difference and i run 92 all day every tank. Call it peice of mind.

[wantmorepower]

You will always here both side to this argument. I think you will have to be the judge for yourself with the gas issue.

As for me, I can tell the difference in the way my car runs from running the cheap stuff and the 93 octane premium.

[Turbo V6 Camaro]

me to and even thou i use the same gas EVERY DAY, if i get crapy gas is really makes me mad to say it in a nice way

[firebirdrumble00]

Originally posted by Lon:
but it is a good habit to run higher octane just to keep deposits and such down in your engine.

Keep deposits down...?? trust me regular fuel doesn't leave deposites in your engine unless something else is going wrong...

Originally posted by Lon:
I could be wrong, but this guy could break down timing on a 69 mustang from memory. so i took his word for it. LOL

What is this "break down the timing" i've never heard of that ever?

Originally posted by viper:

higher octante fuel lets you advance the timing more with out detination, advance the timng you make more power, but do it to much and it tries to push the piston down went its still coming up (knock) or detination, so running higher octane will stop that as higher octane is harder to ingnite and bruns for a longer time,

okay man not bad info "but do it to much and blah blah blah" no kidding dude advancing the timing by definition means firing the plugs farther before top dead center.

Just because high octane has a slow burn does not mean it is harder to ignite infact it is easier to ignite a lottttt easier. Do you know what they do to increase the octane in the first place, they used to add lead (b.c. it was very cheap) until catylists became the law. Today what they add is alcahol, propane (BBQ grills), and butane (what is found in lighters). Hope this clears some things up for you.

Anywho I agree with Viper on the computer controlled timing not much you can do without a chip and it is rendered useless to use higher octane on a normal motor.

[dcrow23]

I switched from 87 to 91,much better

[andrew.brandon]

I beleive you also haft to look at the different gas stations. I am sure everybody has heard this before but every group, sheets/shell/mobil, gets their gas from the same place. Not quite sure what it is called off the top of my head. Anyway, from there they add their own mix into the gas to make it perform better. Not saying this is always true but, the cheeper the gas the less of their stuff in it, which provides less performance. The octane stays the same but it is performance and economy that we get from this stuff they add. Every car is in a different location so which is best for the car must be tested. Don't just choose a gas station just because that is where your parents get their gas. I myself have noticed that Sheets is really cheep in my area. 15cents cheeper per gallon. But I get the same performance with 91 octaane from sheets as I do with 89 octain mobil and the same performance with 87 octain shell. Guess which one I buy.

[Turbo V6 Camaro]

i'm a shell fan too, shell all the way, my buddy all he used was shell and when he took his motor apart it was vary vary vary clean for having 10,000 REALLY hard miles on it and 12 set of back tires wasted from those hard miles, and that only driving the car 4 months out of the year

[FloydSummerOf68]

All I ever use is shell...usually 93....89 if I dont have much cash

[Lon]

who pissed in firebirdrumbles wheaties. By breaking down the timing, i was saying that from memory he could tell me what the timing should be on his mustang. Ergo saying that he knew what he was talking about on cars and had been doing it since before i was born. I was just throwing in my 2 cents. This is a forum. Thats what its here for. No need to show your supremecy of car knowledge.

[wilkcamaro98]

so guessing wawa gas is prolly on the lowerend of that quailty thing of addin there on mix of stuff?