Octane question
Pro
Joined: Jan 2008
Posts: 584
Likes: 1
From: Near Lockport NY Black 1986 Coupe
Lovely, another octane debate. 
If your sensor is working, running 87, there will be no signs of knock at all unless at WOT. The compression of the 94 LT1 is 10.5:1, correct? It is completely possible to run 89 octane in this motor without any loss in performance, as long as you don't install aftermarket CI heads on it. I wouldn't get anything higher than 91 just because you really don't need it.
If your sensor is working, running 87, there will be no signs of knock at all unless at WOT. The compression of the 94 LT1 is 10.5:1, correct? It is completely possible to run 89 octane in this motor without any loss in performance, as long as you don't install aftermarket CI heads on it. I wouldn't get anything higher than 91 just because you really don't need it.
Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
The engines that have "premium recommended" don't have any limitation on 87 octane -- the knock sensors will cut back on the timing, and HP, and there will be no detonation.
There is no problem running 87 octane in a STOCK engine that has "premium recommended."
Since the LT4 says "premium required", it will not cut back enough -- you need high octane.
Tom Piper
There is no problem running 87 octane in a STOCK engine that has "premium recommended."
Since the LT4 says "premium required", it will not cut back enough -- you need high octane.
Tom Piper
Burning Brakes
Joined: Feb 2008
Posts: 1,168
Likes: 17
From: Iowa
Safety Car
Joined: Oct 2007
Posts: 3,816
Likes: 0
From: :45 minutes from everywhere / E-I-E-I-O
If ya' gotta' run low octane, either have the burn timing retarded in the computer (you'll have to reverse it if you go back to hi-grade),
...
OR, you can jump the AKS so that the timing stays at the default retard setting (which will set a code/light).
...
OR, you can jump the AKS so that the timing stays at the default retard setting (which will set a code/light).
Instructor
Joined: Apr 2003
Posts: 197
Likes: 0
tixeon, check post #4 in this thread. Jon (FICINJECTORS) is an expert and vendor for injectors so I take what he says as fact. I know GM only recommended their fuel treatment as the only acceptable one for 1988-89 Vettes
http://forums.corvetteforum.com/show...ight=Injectors
http://forums.corvetteforum.com/show...ight=Injectors
Last edited by seenalot; Jun 3, 2008 at 11:12 PM.
Melting Slicks
Joined: May 2007
Posts: 2,382
Likes: 2
From: Kathleen FL
If you do that, you will only be set at base timing with no timing advance when throttle applied. The result, pop, backfire, bang, slow running, glowing exhaust manifold, chitty bang bang chitty chitty bang bang.
Burning Brakes
Joined: Jul 2007
Posts: 751
Likes: 0
From: Eau Claire Wisconsin
The 87 octane runs well in my 94. Its my DD and don’t really push it but really never heard any ping either. But the real questing is the 10% methanol (alcohol) blend that is now coming out. In FL I don’t know why they are pushing it so hard at this time.
Has anybody experienced a decrease in mileage or performance problems?
Has anybody experienced a decrease in mileage or performance problems?
Last edited by GS4-LT1; Jun 4, 2008 at 06:22 AM.
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Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
Ethanol has a higher octane rating than gas, but less BTU content (energy) per a given volume.
Therefore, to do the same amount of work, it takes a greater volume of ethanol and thus less miles per gallon.
Tom Piper
Therefore, to do the same amount of work, it takes a greater volume of ethanol and thus less miles per gallon.
Tom Piper
Burning Brakes
Joined: Jan 2006
Posts: 805
Likes: 1
From: Jacksonville Florida
My line of thinking is this, yes regular or mid grade may be cheaper. However, if the question is, will it cause damage? The next question is, if so, will I save enough to pay for my engine rebuild? Probably not. Is saving a couple of dollars at fuel up worth the risk? Not really.
God luck with whatever you decide!
Safety Car
Joined: Oct 2007
Posts: 3,816
Likes: 0
From: :45 minutes from everywhere / E-I-E-I-O
The only thing I've ever heard of that lights up the exhaust manifold is timing that fires the air fuel with the exhaust valve open.
With spark at 0, or 2 btdc, the ex. valve isn't even close to opening. Nor is the intake valve.
Slight loss of power is all that will be noticed by by-passing the AKS. And the DTC for "timing retarded too long".
Can you explain a little more here??????
Last edited by schrade; Jun 4, 2008 at 01:03 PM.
Melting Slicks
Joined: May 2007
Posts: 2,382
Likes: 2
From: Kathleen FL
How is all this???
The only thing I've ever heard of that lights up the exhaust manifold is timing that fires the air fuel with the exhaust valve open.
With spark at 0, or 2 btdc, the ex. valve isn't even close to opening. Nor is the intake valve.
Slight loss of power is all that will be noticed by by-passing the AKS. And the DTC for "timing retarded too long".
Can you explain a little more here??????
The only thing I've ever heard of that lights up the exhaust manifold is timing that fires the air fuel with the exhaust valve open.
With spark at 0, or 2 btdc, the ex. valve isn't even close to opening. Nor is the intake valve.
Slight loss of power is all that will be noticed by by-passing the AKS. And the DTC for "timing retarded too long".
Can you explain a little more here??????
Usually your advance at idle is about 20 degrees because the computer adds about 14 degrees on for proper operation. Light to mid, up to full throttle, the computer can add anywhere from 14 - 36 degrees to base timing for proper cylinder pressure to get the car moving.
I'm talking about TPI cars with HEI distributers. Dunno if that applies to LT1s, but I'm sure the concept is similar.
Racer
Joined: May 2004
Posts: 295
Likes: 3
From: Newton NJ
I would stick with the higher octane! I tried to run 87 octane in my 87 and it started to ping under load. Even trying to baby it would, ping on tip in of the throttle. I promptly put some 93 octane in and I'm just starting to get my performance and mileage back.
I think the lowest you can go on octane is 91 in these cars or least for the L-98's. Of course your mileage my vary, just the results of my experiment.
I think the lowest you can go on octane is 91 in these cars or least for the L-98's. Of course your mileage my vary, just the results of my experiment.
Advanced
Joined: Apr 2007
Posts: 66
Likes: 0
From: So. Orange Co. Ca.
Just checked the fuel door on my '84 LT-1 - says "unleaded fuel only" - "premium fuel RECCOMENDED" (in english & french
) Been using 87 octane since I bought it last year - 12k miles - no ping - runs smooth. It's my DD - life is good!
) Been using 87 octane since I bought it last year - 12k miles - no ping - runs smooth. It's my DD - life is good!
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
On average, premium is about 20 cents higher than regular unleaded. If you buy say 15 gallons, that's $3. Go to Starbucks one less time a week and you've paid for the difference. We all really need to stop second guessing the pennies we save on lowering octane and start writing our representatives and insist that the oil companies be held accountable for their gouging of the American People