Quick question about gas
Thread Starter
2nd Gear
Joined: Jul 2007
Posts: 2
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Quick question about gas
I recently bought a 1988 corvette. I recently fixed a steering fluid leak, so now I have the car running. But I wanted to know what octane gasoline do you guys use on your C4's. Or if one of you guys has the owner's manual, what's the manufacturer recommended octane?
Melting Slicks
Joined: Dec 2004
Posts: 2,954
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From: Obama=death for America
You can use a minimum of 87 octane. The timing will be automatically retarded a bit via the computer, due to the lower octane and power will be reduced a bit, but nothing detrimental will occur. If you should hear pinging, fill your tank with a higher octane as soon as possible.
Actually, very slight pinging (barely audible) is optimum, but most
people don't like to hear anything (me included), so if you dump a few gallons of 93 in the tank, it should go away.
Actually, very slight pinging (barely audible) is optimum, but most
people don't like to hear anything (me included), so if you dump a few gallons of 93 in the tank, it should go away.
Race Director
Joined: Jul 2004
Posts: 16,795
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From: Lake Havasu City, AZ
an 88 is approaching 20 years old. As cars age octane appetite often increases. So whehter it runs without knock on 87 now depends on the condition and mileage of the engine.
As engines accumulate mileage they can also accumulate internal carbon deposits and varnish. Deposits that form on the pistons and combustion chambers can change the shape, surface and volume. Rings wear, permitting blowby, etc etc.
To this extent compression and other changes can induce pre-detonation (ping or knock)
While a new engine may be fine on a diet of 87 octane, an afflicted engine may require an increase in octane. a colleage has a 94 VW Jetta with 190K on the odometer. When new and until it hit 100K, it was happy on 87. As it past 120K it needed 89 0ctane. Around 170K miles it was no longer knock free on 89 and now happily only runs on 92-93
As engines accumulate mileage they can also accumulate internal carbon deposits and varnish. Deposits that form on the pistons and combustion chambers can change the shape, surface and volume. Rings wear, permitting blowby, etc etc.
To this extent compression and other changes can induce pre-detonation (ping or knock)
While a new engine may be fine on a diet of 87 octane, an afflicted engine may require an increase in octane. a colleage has a 94 VW Jetta with 190K on the odometer. When new and until it hit 100K, it was happy on 87. As it past 120K it needed 89 0ctane. Around 170K miles it was no longer knock free on 89 and now happily only runs on 92-93
Safety Car
Joined: Nov 2005
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From: W MI
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Drifting
Joined: Nov 2002
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From: 2003 Points Champ Great Lakes Corvette Challenge; 2006/2007 Winner MSD True Street
why would you use 87???
The computer will adjust, yeah
By why would you freaking want your car to adjust to 87???
It's a vette, not a school bus.
I drive a vette, it looks cool, but I intentionally retard performance because I want to save a few bucks????
Com' on guys!
Matt383
Drifting
Joined: Nov 2002
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From: 2003 Points Champ Great Lakes Corvette Challenge; 2006/2007 Winner MSD True Street
I can say that my truck manual suggests that when towing or doing other stressful things with the truck I should use a higher octane.
This would suggest that the engine needs more octane under load.
So my rationale would be if you don't put your vette under load (WOT a lot) you may not notice.
My two cents.
Matt383
Large Impressive Member
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Race Director
Joined: Jun 2004
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From: WI
The knock sensor hears ping that the human ear cannot.
I track mine and do not want to risk damage from saving a little bit in gas cost. I would like to datalog the car to see when there are knock counts but I do not have that equipment yet. So better safe then sorry for me.
I track mine and do not want to risk damage from saving a little bit in gas cost. I would like to datalog the car to see when there are knock counts but I do not have that equipment yet. So better safe then sorry for me.
Heel & Toe
Joined: Jul 2006
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I have an 89 with the L98 and never run anything less than 91. If I can get the 104 Sunoco I'll always buy that. And I get much better gas milage with a higher octane. Just made a run to Richmond and back from Cincinnati and averaged 28.4 with 93 octane.
Drifting
Joined: Nov 2002
Posts: 1,905
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From: 2003 Points Champ Great Lakes Corvette Challenge; 2006/2007 Winner MSD True Street
Now to the other extreme
If your l98 is even close to stock you don't need the 104.
That is just wasting your money.
Your car was designed for premium, not race fuel 104.
The only way an engine can benifit from 104 is having higher compression.
If you have stock compression you will never benefit from 104.
Sunoco 100 costs $6.47 a gallon around here.
Why use it if you don't need it?
Save your $$$ and stay with 91 - 94 Octane.
My two cents.
Matt383
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
My 1989 owners manual says 91. Your heads are the same as mine so you should run at least 89. I mix 93 and 89 in the hot summer months 50/50 to approximate 91 octane and it runs very well. These engines evolved over time so a 1987 and say a 1990 can be very different.
Le Mans Master
Joined: Dec 2002
Posts: 6,715
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From: Santa Teresa New Mexico
Gas is like beer, you can't own it. Buy whatever is on sale at cheap chicken charlies.
87 89 91? I remember a time when it was 110 or nothing.
110 is red, the shizt they sell now looks like water, but it doesn't need lead to contain the burn rate.
Premium is a racket, it all comes in the same tanker, at the same time, from the same fuel depot.
87 89 91? I remember a time when it was 110 or nothing.
110 is red, the shizt they sell now looks like water, but it doesn't need lead to contain the burn rate.
Premium is a racket, it all comes in the same tanker, at the same time, from the same fuel depot.