87 or 94 octane

[Old Dodge Dude]

Hi folks any thoughts on what grade of fuel to run in a 62 valiant. 225 slant 6. Any and all info would be appreciated

 

[wawarnick]

If it is a stock engine in good tune, 87 octane would be all it needs

 

[rumblefish360]

100%!!!

 

[Demonracer]

Run 87 octane and read the plugs, that will tell you if you have to do some tuning.

 

[Dana67Dart]

Here at 5000 feet in Colorado we have 85, 87 and 91, My 67 Dart stock 2bbl 273 runs fine on 85. My 2006 Dodge minivan which calls for mid grade will ping on 85 but run fine on 87

Due to the altitude (lower air pressure) 85 = 87, 87 = 89, 91 = 93

Run 87, listen for pining, if none your good, looking at the plugs as mentioned above will tell you a lot if you you know what to look for.

 

[AJ/FormS]

Check the cylinder pressure.
anything less than 150 should be able to run 87.
Slantys usually run 145 or less so, they'll run on almost anything, especially in a lightweight car.
By relating it to pressure, this automatically compensates for altitude changes.
If you have a tired old oil-burning clunker, then that oil in the chambers, could initiate pre-ignition, leading to detonation, and requiring more anti-knock in your gas. Don't confuse this type of situation.

 

[Old Dodge Dude]

If it is a stock engine in good tune, 87 octane would be all it needs

Thanks much wawarnick

 

[Old Dodge Dude]

Thanks much Eh

 

[Old Dodge Dude]

Check the cylinder pressure.
anything less than 150 should be able to run 87.
Slantys usually run 145 or less so, they'll run on almost anything, especially in a lightweight car.
By relating it to pressure, this automatically compensates for altitude changes.
If you have a tired old oil-burning clunker, then that oil in the chambers, could initiate pre-ignition, leading to detonation, and requiring more anti-knock in your gas. Don't confuse this type of situation.

 

[Old Dodge Dude]

Thanks AJ/Form

 

[wawarnick]

Thanks much wawarnick

You are welcome