TantalizingSS

Hail,

I was arguing with an co worker of mine regarding 91, 89, 87 octane. He ask me why do I need to put 91 octane on your Camaro. His questions was that " is 91 octane a necissity for your vehicle and this guy uses 87 on his 2007 lexus. What's your guys thought on this?

jmm98LS1

iTrader: (28)

Yes you need to run 91 octane in your car because it was tuned from the factory to run on 91. If you put lower octane gas in it will absolutely run, but the computer will pull timing to avoid detonation which will reduce power output. Plenty of info on this board about octane and what it is/does, do some searches and you'll have lots of ammunition to back up your argument with your coworker.

miked003

i dont know about how they come tuned but i tuned mine with a hypertec to run on 87 this will decrease my power a bit but i think i have enough and gas costs enough $$$. if you run 87 when its tuned to 91 it will create a pinging sound beacuse the gas isent igniteing on time. this is very hard on your. car if you ever start to hear these run it on 91 right away

Formula413

iTrader: (1)

The reason LS1/LT1 engines call for premium fuel is because of the high compression ratio, which makes them more likely to knock. The higher octane fuel has higher knock resistence. And as was said before, these engines CAN run on 87 octane, but this will result in reduced power.

2001NBMZ28

Different vehicles/engines are different - go with the recommended fuel octane in the owners manual. I run 93, it's only about 10 cents difference/gal.

2002_Z28_Six_Speed

iTrader: (19)

Even if you pull timing you won't make good power on low test. It is all about compression ratio.

Another misconception is people with **** cars think putting high test will magically transform their car. Waste of money.

cherryelky305

iTrader: (2)

http://www.automotiveforums.com/vbul...d.php?t=452828

TantalizingSS

Hmmmm, so basicalyy, The higher the octane of the gas - the harder it is to ignite?

dailydriver

He sounds like another uppity snooty, knows NOTHING about cars, Lexus lemming. I sense (but could be wrong) an attitude of ,"well my 'epitome of perfection' Lexus only needs 87, so why does your P.O.S., mulletmobile lowly Chevy need 91?" F*** the yuppiedrone, use 91 and then show him why by blasting his TOYota's doors off!!

cherryelky305

iTrader: (2)

in the world of compression yes. its really that 87 ignites faster when it is being compressed, than 92. 92 is able to be compressed more than 87 before igniting.

NHRAMAN

iTrader: (1)

The Lexus must be lower than 10:1 compression then. Lower the compression, less octane is needed in Naturally Aspirated vehicles.

Formula413

iTrader: (1)

Gas companies are largely to blame for that, they make people think that premium is somehow "better" than regular through marketing, and you just cannot tell some people otherwise. Most people don't know anything about cars.

TantalizingSS

So since our engine compression is above 10 to 1 and if I want to throw in a Supercharger, the motor has to run very low amounts of boost?

cherryelky305

iTrader: (2)

I think thats why motors made specifically for boost applications have low compression numbers. Because once that boost is added the compression actually rises.

BriancWS6

iTrader: (18)

What most people don't understand about octane is that the higher the rating the better it's ability to resist pre-ignition. It doesn't give you more power just because it's 93 vs 87.

Diesel engines operate by heat of compression. As the piston moves upward on the compression stroke the temperature in the combustion chamber rises. It's this rise in temperature alone that ignites the fuel and air mixture, because there is no spark plug to ignite it.

In gasoline engines we do NOT want this to happen. We need the fuel to be stable enough to withstand the heat and the amount it's being compressed so we have as much of the fuel there to ignite when the spark plug fires.

To put it simply if your engine is running fine with no pinging or knock-retard on 87, then you will see no gains or benefit from running 93. If you have an engine like an LS1, or other engine with higher compression and more aggressive timing tables, you will need to run higher octane.

Now here is where a lot of people get lost...the most power is made using the lowest octane without seeing pre-ignition. Use higher than you need, and you could actually lose power. I get funny looks from old school guys all the time when I tell them my 11.34-1 SCR heads/cam car runs perfect on 93, and that I have NEVER ran "racing" fuel in it.

2002_Z28_Six_Speed

iTrader: (19)

Are you talking about the Shell commercials underwater with everything fine and dandy because you used V-Power? You know that you are saving 1000s of clownfish each time you fill up with V-Power!


The only thing I can think of is that with cheaper gas there might be buffers that they use to cheapen it up. Like methanol or some other chemical. [Would that be cheaper though?] That would be the only way you might be less MPG from low test. But that means there are variables in this. Not comparing the same thing...

Formula413

iTrader: (1)

Excellent post, should be a sticky. Especially the last point, that is very true even though it might seem counter intuitive.

Formula413

iTrader: (1)

That's true, it's not always comparing apples to apples, because they may use more/different additives in their premium gas so they can pass it off as "better" rather than just different in application.

I haven't seen that commercial you're talking about but that sounds like something they would say. If you really want to help the environment, use the gas that will run most efficiently in your car. Better mileage=less pollution.

RPM WS6

iTrader: (3)

You will lose power and MPG if you run higher octane in an engine that only needs 87.

conde'strans

iTrader: (8)

If your friend can afford a '07 Lexus and uses 87 octane gas, he's probably just a cheap ***hole! My brother's '05 Audi states 91 octane fuel only. I bet your friend's car does too. 91 octane fuel is all that touches my '98 transam.