DartSwinger

Hey this might be a dumb question but does anybody know which grade of fuel is best to use for old engines? what was the octane rating forty years ago compared to now? Just wondering.

blue 68 gts

Leaded / Premium 93+


Nowadays, there so many additives to our gasoline to make fuel mileage "better". It's aimed at cars that get higher miles per gallon, as compared to our old rides, and older trucks.

Back in the day everything was leaded.... now a day, lead will mess up the computer readings... Non leaded gas doesn't have a high enough octane rating and will cause pinging

Polaradude

I like medical grade NOS...oops wrong gas
Ya what Nick said.

samuelcosmo76

yeah my slant six pings like crazy with the cheap stuff.

1966sportfury

wow that weird what is your 6? 10.5:1 comp ratio? or got the timing off

78D200

I ran my 74 J10 on 87 with no issues minus with the guy driving it.
I ran my 78 D200 on 87 as well with great results minus with the guy driving it.
Now with my 68 Valiant, I run that on 87 (might through a tank of 91 into though) and it too runs great, minus the guy that owns it.

There seems to be a common "opportunity for improvement" there.

67 GTX

what engine do you have?
a /6 can use the 87 stuff

DartSwinger

got a 318 in it. original two barrel. she's almost like she was when my granddad bought her.

78D200

I would run it on mid-grade gas and adjust the timing a little.

DartSwinger

adjust the timing? I got the engine running tdc (factory specs), would i advance it or retard it?

mopardrt

my swinger runs great on regular and even better on premium

1966sportfury

if its pinging you would want to retard it,
if its an everyday driver i tune by ear

rexus31

That is a false statement. Leaded/Unleaded has nothing to do with Octane Rating. I worked at a gas station in the late Eighties and we sold 89 Octane Leaded. See this link for High Octane Unleaded Fuels:

http://www.sunocoinc.com/site/Consum...UnleadedFuels/

The Octane Rating has to do with the fuels propensity to auto-ignite. The lower the octane rating, the greater the chance of the fuel auto-igniting under high compression. This is what causes the pinging. The fuel ignites before the spark plug fires.

1966sportfury

you are right but.................. i can see a octane fued!!
can i give my 2cents? 85 octane has a higher btu burn rate per gallon than 92, 92 burns cooler but producess a higher "explosion" (do i dare say) too high of octane can actually hinder power,

67Polara

i always ran 87 octane in my Polara had a 318 in it never made any weird sounds. but my 06 mega cab with the 5.7L Hemi makes funny nioses on 87 =p so i dunno

rexus31

You are absolutely right. It's also about dissipating heat. More heat in an old cast iron V8 usually equals detonation (pinging). The cooler burn rate also helps fight detonation.

You shouldn't run a higher octane than your motor is rated for. My '07 Charger R/T is rated for 89 Octane. If I run anything higher the car runs a little sluggish. I can reprogram my car for a "91 tune" which would advance the timing necessitating a higher octane. It's not the higher octane that gives me more power, it's the timing advance. The higher octane is needed to prevent detonation.

67Polara

the sunoco site's intro sounds like the back of a pack of Camel cigarettes LOL