Regular Plus or Premium gas
04-01-2017, 10:16 PM
#21
My opinion - how much do you drive the car? If it just sits a lot, go with ethanol free mid or premium. Always available near a lake (boats). If the extra $ is a problem you probably shouldn't own a Corvette
04-01-2017, 10:37 PM
#23
Team Owner
Putting fuel of the wrong octane (for what your engine needs) is not good for the engine or your wallet. Anyone who thinks that more expensive fuel must be an 'improvement' doesn't understand what goes on in the combustion chamber.
04-01-2017, 10:43 PM
#24
Racer
From what I understand, using too high of an octane is not good. From what I have read, for my 81 which has very low compression, using higher than 87 octane creates a lot of carbon or something, I know I m not much help, I am still learning.
04-02-2017, 03:15 AM
#26
Safety Car
Member Since: Sep 2011
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I have the same motor L-36.
Premium 93 or the motor diesels on 87.
I don't drive her everyday so at fill up she gets the best.
No issues with pinging or surging.
I can drop down to 15mph in a school zone in 4th gear and pull out up to cruising speed with ever down shifting.
You have a 10.25 :1 compression motor.
Feed that beast.
Marshal
Premium 93 or the motor diesels on 87.
I don't drive her everyday so at fill up she gets the best.
No issues with pinging or surging.
I can drop down to 15mph in a school zone in 4th gear and pull out up to cruising speed with ever down shifting.
You have a 10.25 :1 compression motor.
Feed that beast.
Marshal
04-02-2017, 05:48 AM
#27
Racer
Thread Starter
I have the same motor L-36.
Premium 93 or the motor diesels on 87.
I don't drive her everyday so at fill up she gets the best.
No issues with pinging or surging.
I can drop down to 15mph in a school zone in 4th gear and pull out up to cruising speed with ever down shifting.
You have a 10.25 :1 compression motor.
Feed that beast.
Marshal
Premium 93 or the motor diesels on 87.
I don't drive her everyday so at fill up she gets the best.
No issues with pinging or surging.
I can drop down to 15mph in a school zone in 4th gear and pull out up to cruising speed with ever down shifting.
You have a 10.25 :1 compression motor.
Feed that beast.
Marshal
04-02-2017, 05:51 AM
#28
Racer
Thread Starter
04-02-2017, 06:00 AM
#29
Racer
Thread Starter
Also when i owned my 69 350/350 i only used regular unleaded not because i was CHEAP. And it ran great all the time . Now that i have a 68 L36 i just wanted to be sure of the right gas for my big block. Apparently there are mixed thoughts about this. So i will just be putting premium in all the time.
04-02-2017, 07:19 AM
#30
Race Director
Octane measures a fuels resistance to detonation.
Low octane: Wants to burn. Takes lower energy to ignite it.
High octane: Does not want to burn. Takes more energy to ignite it.
Think of it in terms of 'units' and for arguments sake we'll talk about pump gas and assign a maximum number of 100 units. 87 octane takes 87 units of energy to ignite leaving 13 units to power the engine. 93 octane takes 93 units to ignite leaving 7 units to power the engine. 87 yields more energy than 93.
SO..if 87 yields more energy than 93 then why do high performance engines (high compression) need higher octane? As the piston compresses the air/fuel molecules they rub against one another and create friction. This friction creates heat. If enough heat is created from the molecules rubbing together the air/fuel mixture will self detonated with NO spark from the plugs. This is pinging/knocking/pre-detonation. High octane fuel does NOT want to burn thus it can resist self detonation from heat friction.
Low octane yields more power
High compression yields more power.
From a performance perspective higher compression always wins out over lower octane.
If you run high octane fuel (does not want to burn) in a low compression engine the spark energy isn't sufficient to ignite and burn all fuel. The end resist is excess carbon build up. Build up enough carbon and compression ration goes up and you'll need high octane gas.
04-02-2017, 07:43 AM
#31
Racer
Thread Starter
You are correct.
Octane measures a fuels resistance to detonation.
Low octane: Wants to burn. Takes lower energy to ignite it.
High octane: Does not want to burn. Takes more energy to ignite it.
Think of it in terms of 'units' and for arguments sake we'll talk about pump gas and assign a maximum number of 100 units. 87 octane takes 87 units of energy to ignite leaving 13 units to power the engine. 93 octane takes 93 units to ignite leaving 7 units to power the engine. 87 yields more energy than 93.
SO..if 87 yields more energy than 93 then why do high performance engines (high compression) need higher octane? As the piston compresses the air/fuel molecules they rub against one another and create friction. This friction creates heat. If enough heat is created from the molecules rubbing together the air/fuel mixture will self detonated with NO spark from the plugs. This is pinging/knocking/pre-detonation. High octane fuel does NOT want to burn thus it can resist self detonation from heat friction.
Low octane yields more power
High compression yields more power.
From a performance perspective higher compression always wins out over lower octane.
If you run high octane fuel (does not want to burn) in a low compression engine the spark energy isn't sufficient to ignite and burn all fuel. The end resist is excess carbon build up. Build up enough carbon and compression ration goes up and you'll need high octane gas.
Octane measures a fuels resistance to detonation.
Low octane: Wants to burn. Takes lower energy to ignite it.
High octane: Does not want to burn. Takes more energy to ignite it.
Think of it in terms of 'units' and for arguments sake we'll talk about pump gas and assign a maximum number of 100 units. 87 octane takes 87 units of energy to ignite leaving 13 units to power the engine. 93 octane takes 93 units to ignite leaving 7 units to power the engine. 87 yields more energy than 93.
SO..if 87 yields more energy than 93 then why do high performance engines (high compression) need higher octane? As the piston compresses the air/fuel molecules they rub against one another and create friction. This friction creates heat. If enough heat is created from the molecules rubbing together the air/fuel mixture will self detonated with NO spark from the plugs. This is pinging/knocking/pre-detonation. High octane fuel does NOT want to burn thus it can resist self detonation from heat friction.
Low octane yields more power
High compression yields more power.
From a performance perspective higher compression always wins out over lower octane.
If you run high octane fuel (does not want to burn) in a low compression engine the spark energy isn't sufficient to ignite and burn all fuel. The end resist is excess carbon build up. Build up enough carbon and compression ration goes up and you'll need high octane gas.
04-02-2017, 10:13 AM
#32
I thought that question was already answered when you were told a stock L36 from 1969 has a 10.25:1 compression ration. Your other comment about having a 350/350 didnt make sense since a real 350/350 had 11:1 compression ratio and required premium to not ping. Either you didnt hear it pinging or it wasnt a real 350/350.
04-02-2017, 10:58 AM
#33
Racer
Thread Starter
I thought that question was already answered when you were told a stock L36 from 1969 has a 10.25:1 compression ration. Your other comment about having a 350/350 didnt make sense since a real 350/350 had 11:1 compression ratio and required premium to not ping. Either you didnt hear it pinging or it wasnt a real 350/350.
04-02-2017, 11:11 AM
#34
I aggree it looks like a 350/350, you confirmed it by the engine code?
04-02-2017, 12:32 PM
#36
I think several misread my post - if it sits a lot, ethanol gas is not a good choice. It has a short shelf life and will collect moisture and rust your tank, embrittle your hoses, and corrode your carb. It is more costly but I think it is worth not having to replace all those parts
04-02-2017, 12:33 PM
#37
Le Mans Master
I was running premium grade 93 octane to get my engine all sorted out. I have a 9.5:1 compression 355cid and AFR aluminum heads. I have tried reducing the octane requirements since the timing and carburetor settings are done. I'm currently running mid grade 89 octane and it runs great. Next week I'll try a little bit of the regular grade 87 to see if she knocks or pings. Running great on the 89 octane for now. I realize that I could always raise my compression with a head gasket change. My initial goal was to be able to drive on the cheap stuff and survive.
Last edited by Street Rat; 04-02-2017 at 12:38 PM.
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MikesRed68 (04-02-2017)
nothing you drive on the street regularly