Leaded vs unleaded

Just dawned on me that I have not thought of this. In my 55' F head should I be running a lead additive? Currently there is 91 octane in the tank with a bit of marvel mystery.

 

Yes,

if the valve seats have not been replaced with hardened ones, then you need to run a lead additive.

Jay

 

That's the thing, I am not sure but with the milage I doubt they have been. Guess it wouldn't hurt
Posted via Mobile Device

 

just found it in a search, sorry sparky delete this if you want to

 

Really not necessary for anything but if it makes you feel warm and fuzzy go ahead. Not going to hurt anything. Modern unleaded fuels have enough additives in them that exhaust seat recession is really not an issue. When unleaded fuels were first introduced it was indeed a problem, but no longer. Very few "lead additives" have tetraethyl lead in them anyway, just additives to fight exhaust seat recession which quality unleaded fuels have anyway.
Now if you were talking a high compression, high horsepower engine with extremely high exhaust temps that would be a different story.

 

thanks nickmil

 

Why are you running premium fuel in a motor that has less than 8:1 compression? On this motor it will never help and is a huge waste of money! This motor was built to run on crap fuel so 91 octane is not gonna do a thing for it.

 

Because when I got it home I had 5 gals of fresh 91 sitting in the garage and it was all I had. Don't plan on using it all the time, but it was quicker than running down the road and filling a can with 87 at 11pm after a 6 hour road trip

 

On a car with no timing/knock control, you will make more power with lower octane fuels as long as you aren't pinging.

Basically, if you don't ping on 85 octane, you will make less power with 91 octane.

On a 'modern' car with knock control, higher octane will help because it will add timing into it until it pings, then back it off a couple degrees.

 

I use it too.
Usually on a long driving trip or when I go to the dunes.
I just figure it can't hurt anything.

 

thinking on what Mcruff said, the data plate on mine says minimum octane of 68 thats almost water ran about 8 gallons of old stale gas thru mine it didnt even flinch, it was clean gas, but old, had that nasty smell to it, but it ran off of it just fine, just couldnt bring my self to throw it out, gas was like $4 a gallon then

 

O.K. kaiser you got me thinking. This may be a real stupid question. Can you dillute gas with something cheap to lower the octane? Probably wouldn't do it but curious anyway.

 

That would be the old method of rating octane. In todays fuel it would be the equivilent to 87.

 

When the old method of octane rating was used the 68 octane rating would be somewhere comparable to the 80-82 octane rating of low grade aviation fuel. Even though there was a different method of rating it the actual rating would still be low by todays standards.

 

HMM. Thanks Mike, I did not know that. What would that grade typically be used for other than a jeep? Maybe for a tractor?

 

probably could, but what are you going to find to mix with it that is "CHEAP" everything petroulem related is mucho$ priced any automotive paint recently thud

 

You could always use water.

But it really plays havoc with your mileage. R)