Dumb question. gas type?

Hey. running a 71 mav daily driver with a normal up 250. The guy I got it from says he always runs 93 octane in older cars. Will that be ok for my performance and health of my engine? I can always add additive, but I'd like to save my dough at the pump too...

 

i have always used premium in our older cars 73 mav and 72 mach1 stang

 

I run the cheapest gas I can find in my stock cars. No problems.

 

87 octane...in my 347...

 

87 octane.. These cars are set up for the low grade fuel. When you put the higher octane your really just taking away from horsepower.

 

SWEET!!! I LOVE 87 OCTANE!!! it cheap. should i stay away or look for the %10 ethanol stuff or does it matter?> just popped into mind...

 

Ethanol does nothing for your car when you can look for non ethanol. It hurts more then it helps.

 

Regular gasoline in the early 70's when these cars were made was 91 octane. The lower the octane the faster the burn. This could allow the combustion to occur before the piston has completed its compression stroke, thereby driving the piston downward while it is still attempting to travel upward. The '71 250 has a 9 to 1 compression ratio. It is true if the engine does not necessitate high octane, like 110 race gas, the extra octane will not make more power from the engine and is a waste of money. Too low of octane will damage the engine with spark ping, detonation or pre-ignition when using regular 87 octane fuel. Using higher octane you can advance the timing for increased performance whereas using the lower 87 octane you will need to retard the timing and take away horsepower.

 

so in short your saying use 93 octane to not damage my engine with stock compression and timing?

 

he might want to do some research on that before he attempts (oh crap is jamie looking) it... i'm not sure but i believe you have to do a carb upgrade????:16suspect

 

Lower octane is better. You want to run the lowest possible while avoiding detonation.

 

See http://chemistry.about.com/gi/dynamic/offsite.htm?site=http://theserviceadvisor.com/octane.htm
and
http://chemistry.about.com/library/weekly/aabyb100401.htm

I do know last year while driving my Falcon (10.5 to 1 pistions plus heads shaved .020) in Missouri their premium fuel was only 91 octane and my engine made itself heard going up the hills.

 

run the lowest octane that the motor can wont detonate or ping on. it will take testing on your part to figure it out.

 

i usually use 91 and in my opinion it runs better than on lower octane but it may be my imagination