Question: fuel for a 84?

[killain]

I ask questions, some not too great, BUT I have an 1984 L-83 crossfire C-4, and I looked through the owners manual on fuel. It says to use at least 87 octane, 85 if your running high up in the mountains. It tells all about the knock sensor about what kind of gasoline not to use but nothing about what Gasoline TO use. But it doesn't say anywhere what is the recommended octane. Does anyone know what is the right octane to use in a L-83 crossfire ?

 

[Victory Red C6]

I ask questions, some not too great, BUT I have an 1984 L-83 crossfire C-4, and I looked through the owners manual on fuel. It says to use at least 87 octane, 85 if your running high up in the mountains. It tells all about the knock sensor about what kind of gasoline not to use but nothing about what Gasoline TO use. But it doesn't say anywhere what is the recommended octane. Does anyone know what is the right octane to use in a L-83 crossfire ?

How long have you had this car? What ocatance have you been using to this point? Any problems? If not keep doing what you have been. If you looked in the manual and it states to use at least 87 octane then the is probably the minimum octane that should be used. However, if you live in the mountains then use 85 as the manual states. Seems pretty simple to me.

 

[wishuwerehere82]

If you have the base timing set at 10 degrees, and you can still get Sunoco 94 octane in PA. like they used to have, use it. Otherwise I would use as high an octane as you can find. That's what I do. Using a lower octane is going to result in you check engine light coming on due to the knock sensor retarding the spark advance. Stumbling, poor idle, and stalling is what I got when I tried using 87 octane in my 82 L83, especially gas with 10% ethanol.

 

[82ColEd]

When i lived in PA, i always did 93, although everyone was telling me i was wasting money. I tried running it on normal, but got a pinging, rattling when going uphill (which i had to frequently, bwah), so back to 93 i went and it never had an issue..



-Stefan

 

[nelson84]

All that fuel comes out of the same tank in the ground, its all in your head it runs better. You should just buy the cheap stuff and dump in a couple bottles of octane boost.

 

[Hib Halverson]

Man oh man, are there some urban legends posted here.

First, on the octane use in an 84....back then, GM calibrated for 87-octane fuel. As a general rule, under most conditions, provided the engine is not modified, is running properly and is in good condition, 87 (or 85-in high altitude areas) will run fine with little or no knock retard, however, on warm or hot days when you're driving the car hard, I'd move to 89 or 91 to prevent any knock retard and get best performance from the engine

Now, if you want to get real anal about gasoline and you want to know under what conditions, if any, the ECM is skewing the timing with knock retard, you need a scan tester that will allow you to look at the ECM's serial data stream in real time. Road test the car on a cool or warm, but not hot, day and watch the knock input during some wide-open throttle acceleration. If you see KR, go to 89 octane and retest. If it goes away, that's what you need to eliminate all knock retrad. On 89, if you still see KR, go to 91-octane and road test again.

Keep in mind that if the engine controls are working right, the EST system is always working to stop detonation by slightly retarding the spark when detonation is sensed. KR under WOT conditions does decrease performance but at other times some knock and knock retard is of little consequence.

Now, the statement above that the check engine light comes on if the knock sensor detects detonation and retards timing is incorrect. If the ECM gets a KS input, it retards the spark until the knock incident ends but does not turn on the check engine light. Now, if the electronic spark timing (EST) system is not working properly or it fails a self-test, then the check engine light will come on, but that's a function of the system NOT working properly rather than a function of the system working as designed.

Do not use octane boost, for two reasons:
1) Virtually all mass-marketed, canned octane boost products which do not contain MMT, are not capible of a useful increase in octane and are a waste of money.
2) The few canned boosters made with MMT, do work, but they will eventually damage catylitic converters and oxygen sensors. The cost of replacing those parts negates any advantage in boosting the octane of regular gas has over the cost of premium fuel.