Generation III Internal Engine - Whats the max octane i can use?

Ok guys, i usually fill up at 110 octane in my 3rd gen. it never messed it up ( it was a carbed 350) BUt anywho, I just bought a 1998 ss and im wondering if i can put the same kinda gas without hurting it. I get my gas from the airport, they call it av gas... Is it safe?

there really isn't a reason to waste your money on it, unless you had a tune for it

we've put racing gas in our 98 ss. I don't know what octane but i know it's over 100.

if u have o2 sensors the leaded gas will burn em.

If you still have the catylitic converters in it, that octane might take them out. Besides that, I agree with 098z28. It will not give you any more power, and will be a waste of money unless you are running a certain application like a highly boosted, FI application, or you are worried about detonation from running too much timing, or worried that you may have a bad tank of gas from being too old, as the octane level will drop untreaded over a long period of time.

you need tuning to really benefit from it, and say bye bye to your 02's

i have gutted cats, so it will harm the 02 sensors?

i also get a good price on this gas...not wasting any money, actually saving.

you have 4 02 sensors. fronts, which are critical, and you have the rears, for the cats which just throw codes and dont actually effect anything.

it will ruin the fronts and the rears, but seeing as youre are gutted no need to worry about the rears.

yeah I have seen burnt O2s from using leaded race gas like that

Another question, What if the 02 sensors go bad in these things? I took off my 02 sensors on my 3rd gen, Didnt really do anything to it but chec kengine light. But everything ran spiffy....

it will make the car run in closed loop mode and wont a full potential. the o2 read how much air and fuel is in ur exhaust and modifies your fuel vs air to make it run better.

you should get wide bans for the front 2 and get o2 sims for the back 2

it will make the car run in closed loop mode and wont a full potential. the o2 read how much air and fuel is in ur exhaust and modifies your fuel vs air to make it run better.

you should get wide bans for the front 2 and get o2 sims for the back 2

Without the front O2 sensors will run in open loop - it only runs in closed loop if the front 02 sensors are working and warmed up.

Any higher then 94 octane is just wasting your money and power. LS1 typically run best with 91-94 octane, any higher and you begin to loose power due to the extra timing needed to fully combust the mixture, even if tuned. With 91-94 octane, you should be able to run anywhere from 24-29 degrees of timing ... the sweet spot for LS1 to make power. Running higher octane (100 and up) actually slows down the combustion process (this is how octane works, higher octane is less volatile), and if it is too slow the max combustion pressure will not happen at TDC, where it is need for max torque.

this is very good info...Thanks. 20$ a tank is why i get the gas... I guess its back to 35-40$ a tank lol

At $20 a tank i would find a way:engarde:
the AV 101 is 4.50 a gal here,i use it on a boat

dunno how the hell it is saving you money but post up...i would love to get some fuel like htat for less than the cost of premium!!!

av gas designed for high altitude doesn't mess with anything?

I remember going over this a long long time ago on turbobuick.com and I recall the majority saying that it wasn't a substitution for racing fuel.

A motor makes peak hp/tq on the brink of detonation. The further past that you go, the less you make. Basically, run the lowest octane you can run without detonation.

Good stuff HERE (http://p66conoco76.conocophillips.com/gcommon/internet/design/p66Conoco76/docs/FAQ1.pdf)

Av gas is not designed for high altitude. It is 100 octance with lots of lead. It is called low lead, however, it has 8 times the lead of the old 87 octane...

You will not pick anything up from using it....unless your application needs it. Are you a buily high compression motor that is experiencing detonation or knock.....

Then there is no need....get the 93 or whatever is available, and you will make the same power...if not more.

Same goes for 93, if you can run 89 with no pinging or detonation, go for it. You'll get a better burn. However, once you start tuning, tune with the fuel you plan to use constantly.

If I planned on tuning my ls1 to run on a 93/110 mix would it be faster than just 93 or just 100. How high octane can you tune for on a stock engine and make the most power?

If I planned on tuning my ls1 to run on a 93/110 mix would it be faster than just 93 or just 100. How high octane can you tune for on a stock engine and make the most power?

Octane doesn't make the power, it is how fast (violent, yet controlled) the mixture can ignite. Timing controls when that mixture ignites before top dead center (peak cylinder pressure). Higher octane slows the process down. Stick with 93 octane and have it tuned for that, there is no need to go higher the 94 octane on most LS1 N/A engine setups. Unless you run extremely high compression ratios like 12.5:1 and higher, or ridiculous boost levels, or large nitrous jets. Running high octane was usefull to less efficient combustion chamber of the 60's era (SBCs), the LS1 chamber design is very efficient and doesn't require high octane to ignite the mixture more completely.

The highest unleaded octane easily available is about 100 octane, higher then this and most fuels use lead to boost octane, you do not want to run lead all the time in an EFI equipped engine.

anything over 105 octane is leaded. once in a while is ok for performance reasons but running it all the time it will destroy the o2 sensors.

Av gas is not designed for high altitude. It is 100 octance with lots of lead. It is called low lead, however, it has 8 times the lead of the old 87 octane...

there are actuall 6 types of avgas, but the new avgas is rated at 80(red) 100(green) and 100Low Lead(blue). At something like $4-5 a gallon i sure wouldn't be wasting money on it. And if your getting it for 20 bucks a tank, your probably getting the old stuff the airport won't put in the planes. So it's likely stale nasty gas. This is coming from an a+p tech in training.

Resurrecting this OLD dead thread... Octane - how much is too much or how little is not enough...

I completely agree with this statement:

A motor makes peak hp/tq on the brink of detonation. The further past that you go, the less you make. Basically, run the lowest octane you can run without detonation.

BUT - I know the LS1's have a "low octane table" to help avoid knock. Is there anyone that can get technical about this with proven evidence for what the MINIMUM octane is before the car pulls timing or what the Maximum is before you start loosing power?

FWIW I run Shell's 93 octane in a bolt on, stock internal/bottom end. Is there any reason to change? I used :google: but couldn't find anything other than speculation (and this thread)

Guy I bought my car from put regular in it and it ran poorly. I ran 93 only in it, and then had it tuned. when we had the hurricane and there was no gas, I put in a few gallons of 108 or something like that, and now I get a P0131 code for one of my O2s.

so ill stick with 93

Not worth it at all. Run 91 or 93 in it, have fun.

Even better if you can run 93 without Ethanol in it :)

Even better if you can run 93 without Ethanol in it :)

Why's that?

Seems plenty of people like to use gasoline with ethanol in it (E85) and make more power both N/A and boosted over straight gasoline.

Why's that?

Seems plenty of people like to use gasoline with ethanol in it (E85) and make more power both N/A and boosted over straight gasoline.

E85 is completely different from regular gas. Normal gas is only like 10 percent ethanol. E85 is 85 percent.

E85 is completely different from regular gas. Normal gas is only like 10 percent ethanol. E85 is 85 percent.


Still, if E85 (85% ethanol/15% gasoline) is better than straight gasoline (0% ethanol/100% gasoline) then wouldn't you think that E10 (10% ethanol/90% gasoline) is also better than straight gasoline?

Still, if E85 (85% ethanol/15% gasoline) is better than straight gasoline (0% ethanol/100% gasoline) then wouldn't you think that E10 (10% ethanol/90% gasoline) is also better than straight gasoline?

Your first post implied that E85 and regular gas were the same. That's what I was commenting on. As far as what blend is best, old schoolers will say no ethanol is best. FI guys will say E85. On a stock car I think just premium gas is fine.

...
I completely agree with this statement:



BUT - I know the LS1's have a "low octane table" to help avoid knock. Is there anyone that can get technical about this with proven evidence for what the MINIMUM octane is before the car pulls timing or what the Maximum is before you start loosing power?
...To use the LO table, knock has to be detected...

so be careful to not rely on the LO table and/or the knock sensors

( tune to avoid knock )

To use the LO table, knock has to be detected...

so be careful to not rely on the LO table and/or the knock sensors

( tune to avoid knock )

Good point:thumb: