Since we can no longer buy 92 octane or higher in Arizona or Calif. can I mix 15 gallons of 91 and 5 gallons of 103 and have 94 octane? The Mobile station in town sells 103 octane for 3.95 gal and if it will solve my pinging problem it sure would be worth it. I have checked every thing out and the only thing I can think of is when I had the rebuild done they decked the block and heads and took off too much material and my compresion is too high for 91 octane. The car runs fine but anytime over 210 degrees it will ping under a load.

Thanks

PC


[Modified by Pete Clough, 5:04 PM 11/18/2002]

 

If you are running cats make sure that the 103 octane is unleaded, if not it will clog your them.

 

Should work....but...a shot in the dark.....maybe buy an octane boster from auto supply store????

What do you think.....why do you need such high octane?????

Hi Compression???? OR????

THANKS

fyi

tony

:smash:

 

Yes you can mix the fuel but even if you have removed the cats you still need unleaded because leaded fuel will ruin the 02 sensor. Install a 160 degree thermostat get one of those fan switchs that allow you to keep both fans on all the time. Lower engine temp will help with the detonation. As to the advice to use octane booster that stuff will raise fuel a couple points so if you have 91 octane after the booster you will have 91.2 not worth the money.
Another option is go to a Lowes get a gallon of Xolene add it at a ten percent mix with your fuel. Here in Indiana I pay $8:00 a gal. for it. Xolene is 116 octane DO NOT MIX AT HIGHER RATIO THAN 30% If the engine has a lot of miles run something through it to remove carbon buildup that can help also.
:cheers:

 

With you living out there where it really never gets that cold, I would say going with a 160 degree thermo and whatever method you want to make your cooling fans come on sooner is the way to go. It's a one time change and you never have to worry about it again.

 

I can't find the link, but a few months ago this subject was debated to death and in the thread someone posted a link to a site that explained octane to great depths.

There were mixing tables that were based on the Union 76 fuels available, but it was real good. do a search on the archives and I think you can find it.

 

I'll past the table in a reply if someone can explain to me how to do it. :)

 

In Phoenix, I have 10:1 comp, '84 with one fan, my knock sensor retards the timing instead of pinging. I use octane boster and 92 or 93 gas; 91 is bad news. I run a 160 thermo, fan comes on at 200 and goes off at 180. When its 110 my engine will go to 220 (8 less than factory fan switch) with air on in traffic. And I also have 25% smaller drive pully for the water pump.

 

ttt
Shadypete, Where do you find 92 or 93 octane around Phx?

 

According to the 76 chart 1 part of 100 with 3 parts of 91 gives 93.3 octane.
1 part of 100 with 2 parts of 91 gives 94 octane.
:)

 

Boy - I tried to tell this story last time, but it's so instilled in most minds that high octane means better performance...

Your manufacturer recommends an octane level for your STOCK motor. Increasing the octane will actually lower your performance. Basically, gas is gas is gas, having the same 'energy' potential. Higher octane is required for MODIFIED motors that need the flame front slowed. Check out this site:

http://www.bajajusa.com/Who%20Needs%...ane%20Fuel.htm

I've got buddies that have dyno'd 87 then 93 and showed a loss of power. Using higher octane slows the flame front, actually finishing its detonation of the fuel on the down stroke.

Hope this saves you a few $.

 

In reply to your Ping problem ... I had the same problem with my 85 under moderate exceleration. I used 92 octane fuel. Someone in a forum said he had the same problem, backed off to 89 octane and the ping went away.
A little hesitant, I tryed this and guess what??? Ping is gone!!!!
Who would have fugured????? :eek:

:seeya

 

I agree with what 86VetteBill is saying. You don't need any higher octane than what your car can run with without any detonation.
I think the manual recommends 92 or 93 octane for my LT4. Can't remember exactly right now. Unfortunately here in Arizona our fuel all comes from California. So high test is only 91 octane. So I am concerned about taking care of my engine especially during the summer months.
Another factor contributing to detonation is the temperature of the incoming air charge. The higher the incoming temperature the closer you get to detonation. That's why the blower manufacturers provide pre-coolers. To remove some of the heat introduced by the compressor so the incoming charge is cooler. Other wise they could not prevent detonation without pulling timing.
So here in Arizona a high compression engine may run fine at 85 degrees, but when the temp is up to 112 with 12% humidity there may be a problem.
I plan to do some experimenting some time to see when and if detonation occurs in my engine. But until I do I will add a little 100 octane in the summer just to be safe.
I love the sharing of information that the forum provides. Always something to learn. :)

 

You should go with a 160 thermostat instead of mixing 103 and 91 all the time.
I filled up 10 gallons of 91 and 7 gallons of 100 yesterday and total was $19 for the 91 and $31 for the 100. :eek: (I'm playing with the hypertech. definitely can't do it everyweek)

it's cheper with the thermo in the long run.