LT1's happy with 89 octane gas?

[Cerwin Vega Fan]

When I first purchased my car I ran 87 which basically made it run like crap. I then switched to 93 and now with the HPP+ program installed running 93 is a must (do not turn this into a HPP+ bashing thread). Due to continue anal rape of gas prices I'm considering removing the program and switching to 89 octane fuel, will their be a problem with running this level of fuel? I know most people (including me) like treating their F-Bodys to the best of everything but my wallet is getting kind of thin here. If worst comes to worst I could always run a little octane booster and pick up like half a point lol.

[wolfdogs]

I wouldnt. detonation (continued) leads to severe probs.

[TimeLord]

Not even close,saving $4.00 at the pump and risking a 4k rebuild aint worth it!!!!!!!

[Injuneer]

The Owner's Manual clearly indicates that you can use 89 octane fuel (with stock tuning), and while it may result in reduced power, it will not damage the engine.

The actual octane requirement is determined by many things, including altitude, inlet air temperture, coolant temperature, humidity, carbon buildup, corrosion or deposits on the head coolant surfaces, etc. The only way you can be absolutely certain as to the effects of using 89 octane fuel would be to put a scanner on it, and look for knock retard. If you don't get any, you aren't losing performance. If you are getting knock retard, and it is not at the upper limit programmed into the PCM (~15 degrees), you are not hurting the engine.

What is the altitude where you live?

Buying cheaper low octane fuel, and then adding an expensive can of octane boost would appear to be "false economy".... you're going to be paying more for the octane boost than you would for higher octane fuel.

[TimeLord]

My 1994 owners manuals say,,,,

Use premium unleaded gasoline rated at 91 octane or higher.You may use middle grade or regular unleaded gasoline,but your vehicle may not accelerate as well.The gasoline you use should meet specificationsASTM D4814 in the U.S. and CGSB 3.5 92 in canada.These fuels should have the proper additives,so you should not have to add anything to the fuel.

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Be sure the octane for premium is at least 91[89 for middle grade and 87 for reg.],,,,,,

It is doable,but not highly recommended!!!!!!

[Injuneer]

My 1994 owners manuals say,,,,

Use premium unleaded gasoline rated at 91 octane or higher.You may use middle grade or regular unleaded gasoline,but your vehicle may not accelerate as well.The gasoline you use should meet specificationsASTM D4814 in the U.S. and CGSB 3.5 92 in canada.These fuels should have the proper additives,so you should not have to add anything to the fuel.

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Be sure the octane for premium is at least 91[ 89 for middle grade and 87 for reg.]

I think the manual says exaclty what I said it says . What do you perceive as the risk in running less than 91-octane fuel?

[TimeLord]

Ping if he decides to get on it seriously.

The one time I used 89 the car would ping under hard acceleration or while climing steep inclines[Adirondacks].

What we call marbles or breaking glass.

Getting back to the title,the LT1 may live and survive on low octane gas,it certainly wont be HAPPY!!!!

[wolfdogs]

Ping if he decides to get on it seriously.

The one time I used 89 the car would ping under hard acceleration or while climing steep inclines[Adirondacks].

What we call marbles or breaking glass.

Getting back to the title,the LT1 may live and survive on low octane gas,it certainly wont be HAPPY!!!!

mary put 89 oc. in her 95 z28 by mistake one time......you should have heard the predetonation that went on........ i had visions of perferated pistons......

no way.

[alenstein]

I've used 89 on few ocasions, havn't noticed any detonation altough felt loss of power she would not rev as high and slower accleration.

3.30 for super tonight, almost $50 for a tank, last year paid $32 for the same amount, 2 years ago $29. I don't think I can compete with gas stations any longer. hehehe

[Injuneer]

If you "hear" ping (which is not the same as "detonation".... not sure what "pre-detonation" is) you do have a serious problem. It means the knock suppression system is not working as it is supposed to. Its got the ability to pull 15-degrees of timing, and to recognize prolonged use of low octane fuel.

When I first got my ScanMaster, I took my Formula off its regular diet of Sunoco Ultra 94 to test the performance of the LT4 knock module, and found that the knock suppression system worked exactly the way it was supposed to. And I found that there was appereciable knock retard and performance loss as the octane went down. But I never actually heard "knock" (true detonation). And having driven performance cars for at least 30 years before anyone thought of a knock sensor, I think I have a pretty good ear for it.

It showed me that I could reduce the octane in the winter, with absolutely no knock retard or loss of performance. Would I run low octane fuel? No. But I also wouldn't expect any damage to the engine (at least when it was stock) if I did.

[AmericanZ28]

I ran my car on both 87 and 93 octane and have never noticed the difference. Even at the track, the 87 performed just as well as the 93 (back before they switched to 91). 87 octane is all I used for 4 years straight (High School, College budget). When I had the car scanned before I replaced the Fuel Pump, there was no history of knock. Now that I have a new fuel pump, and ever since it became a weekend car, I've put nothing but 91 octane. 112,000 miles in, and it still runs strong!

[Jeanius]

Is it true that premium fuel also lasts longer because of the higher octane?

[wolfdogs]

Is it true that premium fuel also lasts longer because of the higher octane?

huh? no comprende'

[Jeanius]

huh? no comprende'

Meaning, Ive heard that 91 octane fuel burns slower than 87 and 89

[fastTa]

89 octane (R+M/2 method) will not cause any damage to an otherwise stock 10.4:1 compression ratio Gen II LT1 engine. If you run 89 octane and audibly perceive "pinging", then you have much more serious issues (such as the Knock Suppression system failing like Fred mentioned.

With the PCM given the capacity to pull ~15 degrees of timing, and ruling out extreme temperatures and altitudes, you should never experience pre-ignition or detonation so severe that it will damage internal components.