regular grade vs. premium??
Thread Starter
Burning Brakes
Joined: Sep 2003
Posts: 813
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From: Middle Tn
regular grade vs. premium??
With gas prices going to thru the roof for no reason, my question to everyone is this. Do I have to run premium gas in the 91 like the owners manual and the little stickers say, or can I run regular grade gas in it? It gets much better mileage than either one of our trucks but I can't justify spending the extra 20 cents a gallon. To me that just cancels out the better mileage. I need to know if we can run the regular grade, because right now, the vert is just a conversation piece sitting in the basement looking pretty.
Safety Car
Joined: Feb 1999
Posts: 3,504
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From: Mexico Beach FL
I don't know about the L98, but the STOCK (as from the factory, not modified) LT1 engine can run on any grade.
Using the knock sensors, it will just retard the timing -- which will degrade performance.
With the LT1, premium fuel is "recommended" but no required.
With the LT4, I think premium fuel is required.
With my '92 modified LT1, premium fuel is required.
If it is stock, lift the fuel door lid and look beside the gas cap to see what it says.
Tom Piper
Using the knock sensors, it will just retard the timing -- which will degrade performance.
With the LT1, premium fuel is "recommended" but no required.
With the LT4, I think premium fuel is required.
With my '92 modified LT1, premium fuel is required.
If it is stock, lift the fuel door lid and look beside the gas cap to see what it says.
Tom Piper
Last edited by Tom Piper; Apr 19, 2006 at 02:43 PM.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Cars differ. Your car shouldn't knock because of the knock sensor and the ESC. Regular gasoline, inherently, has more power than premium. If the ESC doesn't pull timing, you could actually see a subtle increase in power with regular. Regardless, it will do no harm.
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Racer
Joined: Oct 2002
Posts: 470
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From: Kingwood TX
I burn 87 in my LT1 & have no problems. I'm a Senior Citizen & drive like one . My car has 157,000 mi. & I imagine the wear lowers the BMEP's a bit. Plus I'm hard of hearing from Piloting Jets for 33,000 hours & can't hear the pinging if my Hearing Aid Batteries aren't fresh.
Being old has the advantage of blocking out all the things that annoy younger people.
Being old has the advantage of blocking out all the things that annoy younger people.
Burning Brakes
Joined: Jun 2005
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From: Hyde Park NY
St. Jude Donor '05
Originally Posted by WEH 2000C5
I burn 87 in my LT1 & have no problems. I'm a Senior Citizen & drive like one . My car has 157,000 mi. & I imagine the wear lowers the BMEP's a bit. Plus I'm hard of hearing from Piloting Jets for 33,000 hours & can't hear the pinging if my Hearing Aid Batteries aren't fresh.
Being old has the advantage of blocking out all the things that annoy younger people.
Being old has the advantage of blocking out all the things that annoy younger people.
Team Owner
Joined: Sep 2001
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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The only way to really know is hooking up a scanner and checking for knock counts from the sensor, you want to run the lowest octane possible in an engine that doesnt lend itself to detonation.
The pulled timing would show as gas mileage drops, but it can be harder to tell if youre borderline.
Midgrade is probably ok for it, you shouldnt need premium.
The pulled timing would show as gas mileage drops, but it can be harder to tell if youre borderline.
Midgrade is probably ok for it, you shouldnt need premium.
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Race Director
Joined: Mar 2006
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From: Sherwood, Arkansas
Originally Posted by Tom Piper
I don't know about the L98, but the STOCK (as from the factory, not modified) LT1 engine can run on any grade.
Using the knock sensors, it will just retard the timing -- which will degrade performance.
With the LT1, premium fuel is "recommended" but no required.
With the LT4, I think premium fuel is required.
With my '92 modified LT1, premium fuel is required.
If it is stock, lift the fuel door lid and look beside the gas cap to see what it says.
Tom Piper
Using the knock sensors, it will just retard the timing -- which will degrade performance.
With the LT1, premium fuel is "recommended" but no required.
With the LT4, I think premium fuel is required.
With my '92 modified LT1, premium fuel is required.
If it is stock, lift the fuel door lid and look beside the gas cap to see what it says.
Tom Piper
Team Owner
Joined: Jun 2001
Posts: 26,196
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From: Orlando FL
St. Jude Donor '08-'09
i tried regular in the vette two times in the 6+ years ive had it. both times it ran like crap (it was stock then too) and my gas milage was WAY down. I found with premium I get more milage out of each tank (a signifigant enough number to pay the premium prices)
Safety Car
Joined: Feb 1999
Posts: 3,504
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From: Mexico Beach FL
Originally Posted by TheAngelOfDeath
On my 92 (LT1) the wording under my fuel door lid reads "Premium Unleaded Fuel Only".
My '92 LT1 states "Premium Recommended."
Wonder why there would be a difference for the same year?
However, since mine is modified, no matter what it says under the fuel lid, I now need premium.
I'll have to check, but I am almost positive my neighbor's '96 LT4 states "Premium Required."
I actually ran 87 octane in my '92 before I modified it many times with no pinging or damage.
Looking at it with my Vetronix Tech-1A, the knock sensors would retard the timing under load and the perfomance was diminished -- but, that is exactly what is supposed to happen.
Tom Piper
Last edited by Tom Piper; Apr 19, 2006 at 05:45 PM.
Safety Car
Joined: Feb 1999
Posts: 3,504
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From: Mexico Beach FL
Here is a direct quote from my original '92 owner's manual:
"Be sure the posted octane for premium is at least 91 (at least 89 for middle grade and 87 for regular). If the octane is less than 87, you may get a heavy knocking noise when you drive. If it's bad enough, it can damage your engine."
Tom Piper
"Be sure the posted octane for premium is at least 91 (at least 89 for middle grade and 87 for regular). If the octane is less than 87, you may get a heavy knocking noise when you drive. If it's bad enough, it can damage your engine."
Tom Piper
with Tom. Midgrade is prolly the best for the lower engines but if your not stock or got a high performing L-T1 or anything higher premium is the way for it
Team Owner
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From: OBAMA IS HITLER
Originally Posted by C4driver99
Midgrade is prolly the best for the lower engines but if your not stock or got a high performing L-T1 or anything higher premium is the way for it
here's the breakdown i would generally go with:
'84-85: 87 octane
86-89: 87, or 89 octane max
90/91: 89, or 91 octane max
92-96 LT1: 91 or 92 octane
as has been said, each car may differe a bit. you'd have to test with an engine analyzer to really know the lowest octane you can run --- for best results.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by Hot Rod 90
here's the breakdown i would generally go with:
'84-85: 87 octane
86-89: 87, or 89 octane max
90/91: 89, or 91 octane max
92-96 LT1: 91 or 92 octane
'84-85: 87 octane
86-89: 87, or 89 octane max
90/91: 89, or 91 octane max
92-96 LT1: 91 or 92 octane
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Race Director
Joined: Oct 2001
Posts: 19,653
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From: Melbourne Florida
Cruise-In IV Veteran
I just went out and looked at my 93...next to the gas cap it says "premium recommended"...below the cap it says to "use unleaded fuel only"...doesn't matter where I live since we don't have any 91 or 92octane premium...oops, one place does...Racetrack is 92 but also 10% ethanol...
Interestingly, below both phrases it is printed in French?...are they all like that or do I just have a Canadian honker?...
Interestingly, below both phrases it is printed in French?...are they all like that or do I just have a Canadian honker?...
Team Owner
Joined: Sep 2002
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From: OBAMA IS HITLER
Originally Posted by CFI-EFI
Interesting! I use 85 octane, exclusively in my 1984. The base timing is set a 14° BTDC and the knock sensor is disconnected. Not only is there no knock or ping, it runs like a scalded dog.
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Pro
Joined: Sep 2001
Posts: 744
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From: Homestead Florida
when i had the lt1 in the car, i used 87 almost exclusively, no knocks...ever, and south florida heat...by the way the engine blowing a head gasket was due to an severe overheat coming back from the keys..not the fuel. When i put the lt4 with the hotcam in, it knocked like crazy with the old 87 fuel that was left in the tank (about 1/4 tank) until I went with 93, which was only a few miles. Soon as I filled up, the knock went away. Also could have been something to do with hooking up the egr on the lt4 though. Anyway, one of those things solved the knock problem either the gas, or putting egr on the lt4. just my experience.