Can I put gas at Octane 87(regular) in my 97 SSEi?
09-05-2005, 05:06 AM
#22
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Originally Posted by tverhein
Dr Jay & Willwren:
Ok, I have listened to the posts here.
So if I continue to burn 87 in my SSEi, I run a risk of damaging components, which in turn could damage the engine if the components are not replaced. I am a pretty 'soft, steady, driver', driving 70 highway miles daily. So what is the probability I will damage components? Is it 25%, 50%, 75% some component will go bad? How quickly will a component go bad? Also, which component would likely to fail first?
Ok, I have listened to the posts here.
So if I continue to burn 87 in my SSEi, I run a risk of damaging components, which in turn could damage the engine if the components are not replaced. I am a pretty 'soft, steady, driver', driving 70 highway miles daily. So what is the probability I will damage components? Is it 25%, 50%, 75% some component will go bad? How quickly will a component go bad? Also, which component would likely to fail first?
Try this another way....If your knock sensor is working properly you can run 87 octane all day without damaging your engine. If your knock sensor is not working you run a risk of damaging your engine.
As for the percentages, there are a lot of variables involved in it. If the knock sensor is already picking up say 15* of false (or real due to some other issue) knock and you get another 10* of 'real' knock, you may be in for some trouble. On the other hand if your knock sensor is working properly and not picking up any false knock there'* about a 0% chance you'll damage your engine by just using lower octane. The knock sensor is the key here.
I've known people who really abused their car and had extremely high miles on it without ever replacing their knock sensor and I have yet to hear of anyone suffering engine damage due to low octane. (longest sentence award?) That doesn't mean it hasen't happened though.
Many people here remember a long debate (fist fight) we had over this very issue. Somehow it seems most of the information has been fuzzied up or totally lost.
09-12-2005, 07:24 AM
#23
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Duffer26: Thanks for the info. I read the same verbage from my manual as well.
Dr. Jay: I understand the 'kncok sensor' is the key. So how do I insure my knock sensor is working correctly?
Additionally, to your point that you have never heard of anyone who suffered engine damage due to low octane fuel, I agree with you here. I have never heard of it either.
Dr. Jay: I understand the 'kncok sensor' is the key. So how do I insure my knock sensor is working correctly?
Additionally, to your point that you have never heard of anyone who suffered engine damage due to low octane fuel, I agree with you here. I have never heard of it either.
09-12-2005, 10:13 PM
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Get a scantool and check for knock while accelerating. Then tap on the engine a few times near the knock sensor with a hammer and check for a reaction. Never done it myself but I hear that'* how to do it
Just to make sure we're on the same line, I'm talking only about our engines. I'm sure there have been plenty of older engines destroyed by someone overexcited at the idea of "free" horsepower 
Originally Posted by tverhein
Additionally, to your point that you have never heard of anyone who suffered engine damage due to low octane fuel, I agree with you here. I have never heard of it either.
09-12-2005, 11:40 PM
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A couple of items for you to ponder;
The PCM holds 2 spark tables;
Good_Fuel_Spark
and
Bad_Fuel_Spark
When the PCM learns there is poor quality fuel being used it will default to the Bad_Fuel_Spark table that uses anywhere from 5 to 8 degrees (average) less ignition timing advance than the Good_Fuel_Spark table.
On that basis you will get lousy performance so it may be debatable whether you will save any fuel at all.
For your Knock Sensors;
There is no fault circuit to indicate whether the sensors (1 for each bank) are functioning. I had a wire fall off my rear sensor...no codes get set to indicate a problem and the PCM won't 'hear' any knock.
Also, you may have sludge build up around the sensors inside the coolant jackets if you have Dexcool which will reduce the sensors sensativity..
If you experience knock, any knock, then that means detonation has taken place which is harmfull, maybe not immediately but it may have a cummualtive effect. The pistons are hypereutectic (cast) with the top ring land high up on the piston for emission purposes. When the pistons fail usually a piece of the piston above the top ring land will break off, almost all of the time it will be in the 1 o'clock position.
You can argue the PCM will protect the engine by retarding timing once knock is detected, but this is a cause and effect scenario...first you experince knock then the PCM takes corrective action. You could in fact incur thousands of instances of detonation on any given day.
The PCM can physically retard 720 degress of timing though the OEM PCM is programmed to retard a maximum of 15 degrees depending on AFR (Air Fuel Ratio).
Let me give you a tip. It might not be detonation that actually kills the pistons but you would be wise to not use traction control or hit the rev limiter. GM also uses torque management settings that are based on AFR, how does 15.9:1 AFR sound to you? Think the pistons like it? Also, as the TCS steps though incremental modes it begins to cut fuel to first one injector, then 2 and after that 3.
Have you scanned your car to know how much Knock Retard you experience? Have you inspected the plugs to see if all the cylinders are burning correctly and that none are lean?
Consider the car holds 17 US gallons and the cost difference per gallon may be $0.20, do you feel the cost delta of $3.40 per tank warrants the risk of doing damage to your engine?
If you cannot afford the correct fuel for your car, either park it and wait for lower prices or sell it.
Cheers,
The PCM holds 2 spark tables;
Good_Fuel_Spark
and
Bad_Fuel_Spark
When the PCM learns there is poor quality fuel being used it will default to the Bad_Fuel_Spark table that uses anywhere from 5 to 8 degrees (average) less ignition timing advance than the Good_Fuel_Spark table.
On that basis you will get lousy performance so it may be debatable whether you will save any fuel at all.
For your Knock Sensors;
There is no fault circuit to indicate whether the sensors (1 for each bank) are functioning. I had a wire fall off my rear sensor...no codes get set to indicate a problem and the PCM won't 'hear' any knock.
Also, you may have sludge build up around the sensors inside the coolant jackets if you have Dexcool which will reduce the sensors sensativity..
If you experience knock, any knock, then that means detonation has taken place which is harmfull, maybe not immediately but it may have a cummualtive effect. The pistons are hypereutectic (cast) with the top ring land high up on the piston for emission purposes. When the pistons fail usually a piece of the piston above the top ring land will break off, almost all of the time it will be in the 1 o'clock position.
You can argue the PCM will protect the engine by retarding timing once knock is detected, but this is a cause and effect scenario...first you experince knock then the PCM takes corrective action. You could in fact incur thousands of instances of detonation on any given day.
The PCM can physically retard 720 degress of timing though the OEM PCM is programmed to retard a maximum of 15 degrees depending on AFR (Air Fuel Ratio).
Let me give you a tip. It might not be detonation that actually kills the pistons but you would be wise to not use traction control or hit the rev limiter. GM also uses torque management settings that are based on AFR, how does 15.9:1 AFR sound to you? Think the pistons like it? Also, as the TCS steps though incremental modes it begins to cut fuel to first one injector, then 2 and after that 3.
Have you scanned your car to know how much Knock Retard you experience? Have you inspected the plugs to see if all the cylinders are burning correctly and that none are lean?
Consider the car holds 17 US gallons and the cost difference per gallon may be $0.20, do you feel the cost delta of $3.40 per tank warrants the risk of doing damage to your engine?
If you cannot afford the correct fuel for your car, either park it and wait for lower prices or sell it.
Cheers,
09-13-2005, 12:43 AM
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verry well said my wife allways tells me to use the cheep stuff but i never do and heck the extra is worth the piece of mind and the better feel when on the skinny pedel
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