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can anyone tell me why we HAVE to use super in the 96 SLS's my buddy drives a '03 CTS and says its ok to use regular unleaded the computor will adjust to it. Is this true or should I stick with the premium grade and forget what he says?
Thanks in advance
 

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You could get away with using Regular according to what I've read. The computer will retard the ignition to handle the Regular fuel. You will loose some performance and possibly a few MPG's, so it's almost a toss up to me unless you do a lot of driving. I personally use Premium in my '97 Eldorado. The Northstar was re-engineered to use Regular a few years ago, but it was after your '96 was produced. There are a few trade off's, so you'll just have to make that decision. Hope this helps ...
 

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And don't forget, computer will adjust only if it senses knocking (and knocking sensor is pretty reliable). Otherwise, in most cases there not gonna be any difference.
 

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Let me simply say, the Bandit and oldgamer are correct. So is Iametarg, follow his advice and do a search. :horse:
 

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I use plain ol 87 octane regular gasoline, I am averging 23 MPG with a highway/city mix and it runs just fine. When I put 93 octane premium, I still get 23 MPG and I have no noticable increase in performance.
 

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I have a 99 SLS and I only use premium Mobil gas in it. The price difference really shouldn't be all that much when you figure out what you pay at the end. When I bought my Caddy, the dealer must have put in regular because it didn't run he same way as when I test drove it (it was close to "E" so I put premium in and let it run a while) so I had to change it over to premium, now it runs great. I suggest the premium since overall, it;s not that much of an increase in price after you're done pumping.
 

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If you don't search for the many threads already discussing this then at least read your owners manual:


"Fuel
Use premium unleaded gasoline rated at 91 octane or higher for best performance. You may use middle grade or regular unleaded gasolines, but your vehicle may not accelerate as well. It is recommended that the gasoline meet specifications which have been developed by the American
Automobile Manufacturers Association (AAMA) and endorsed by the Canadian Motor Vehicle Manufacturers Association for better vehicle performance and engine protection. Gasolines meeting the AAMA specification could provide improved driveability and emission control system performance compared to other gasolines. For more information, write to: American Automobile Manufacturer’s Association, 7430 Second Ave, Suite 300, Detroit MI 48202.
Be sure the posted octane for premium is at least 91 (at least 89 for middle grade and 87 for regular). If the octane is less than 87, you may get a heavy knocking noise when you drive. If it’s bad enough, it can damage
your engine.
If you’re using fuel rated at the recommended octane or higher and you hear heavy knocking, your engine needs service. But don’t worry if you hear a little pinging noise when you’re accelerating or driving up a hill. That’s normal, and you don’t have to buy a higher octane fuel to get rid of pinging. It’s the heavy, constant knock that means you have a problem."
 

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Its this simple theres a reason why super is reccomended for you car. Now do you wanna defy that ok look at it this way whats worth more:
1. Save like 10 to 20 cents per gallons and risk screwing up something inside your motor which could be very costly to fix
2. Bite the bullet pay the increase and get prolonged life outta your engine and its components.

Choice is yours but i dont feel like riskin it.
 

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CadillacETC1997 said:
Its this simple theres a reason why super is reccomended for you car. Now do you wanna defy that ok look at it this way whats worth more:
1. Save like 10 to 20 cents per gallons and risk screwing up something inside your motor which could be very costly to fix
2. Bite the bullet pay the increase and get prolonged life outta your engine and its components.
Choice is yours but i dont feel like riskin it.
The knock sensor is there to prevent the kind of damage you're talking about. If it detects spark knock, it retards the timing to avoid the damage. Knock goes away, and so does the potential for damage. There are lots of people on these forums who only use regular and have zero problems with it. There is no reason to dump the extra 20 cents a gallon into some rich oil executive's yacht fund. Those guys have enough money. The car will run fine on regular in most circumstances, so why not try it? When the tank is empty, put in $5 worth of regular. If you don't like the results, fill it up the rest of the way with premium. Don't take anybody's word for it. Try it yourself and you'll see that there is no reason to pay more for premium.
 

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Using regular will not "screw up something inside your motor". The spark knock sensor will simply detect a knock and the PCM will retard the timing appropriately if a spark knock is detected. I, as well as many others have used regular for many years on the advice of someone who was involved in designing and testing the Northstar and no ill has ever come from it. It ran strong and hard at WOT and milage was unchanged. If you are going to race it and want the absolute top performance, use premium. Other wise, the only difference you will notice is in your wallet.
 

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I've had my car for a bit over a week and two tankfuls of 91 octane (not the ethanol crap, either). I'm averaging 24-25 MPG at 75MPH, 90% highway miles.

I just bought 3/4ths tank of 85 octane. Mileage seems to be lower, but it's also quite a bit colder outside. I expect a 10% drop in MPG from the weather alone.

From the seat of my pants, I can't tell if performance (e.g. WOT) is suffering.
 

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If your knock sensor goes bad then it would have a very hard time idleing, if it can idle at all. The knock sensor is always in use whether you use regular or premium. The chances of it going bad when using regular is the same as the chances of it going bad when you're using premium.

87 octane gas ignites faster than 92 octane. So the timeing would be advanced for the lower octane. Since 87 octane burns and ignites at a lower temperature it has a lower expansion rate than 92. Which is what gives you the drop in power. The injectors would have to compensate for the loss in power by putting a little more fuel into the chamber at one time, resulting in the drop in MPG. Even with the extra fuel in the chamber to help push the piston down. It still wouldn't have the same amount of power as 92.

BUT, no problems would occur because of using 87.
 

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You guys have this all wrong. The ONLY difference between 92 & 87 is the octane rating. Octane is nothing more than a measure of the fuels ability to resist spark knock. They do not burn at a different rates. 92 does not provide more power. Both have the same BTU output. Neither one burns cleaner. These are all myths that Shell Oil would like you to believe.

CadillacETC1997, I don't know where you are getting your information from but it is wrong. Burn premium if it makes you feel better, but it is NOT neccassary and you WILL NOT damage your engine by using a lower octane rating.

If the knock sensor went bad (very highly unlikely), the engine would ping, not immediately self distruct. You fix the sensor and move on. You are waaay to paranoid and misinformed about this.
 

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You're right that boosting octane does not boost power, but the effect that lower octane preignition has on the N* timing does affect it! When the KS detects pinging, the ignition is retarded to correct the "problem". This change moves the curve outside of the optimum range.
An old racer's trick is to advance the timing until the engine pings and then back it off a tad.
 

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When youve had the car for 2 weeks and had the motor already blow due to a major oil leak cause of a loose line and none of the idiot lights came on then youd prob be worryed about losein another N* Yes this was an oil issue not a fuel issue but still it was in the shop for 3 weeks and i was forced to drive a Rental Buick Park Ave. (wow for a 35 grand car the thing was noting to brag about)
 

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No arguement there EcSTSatic. That is understood but I would bet it is not detectable by the "seat of the pants dyno".

My only point is you can use regular. You most likely won't notice any difference at all and you definately will not harm anything.
 

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Ranger said:
You guys have this all wrong. The ONLY difference between 92 & 87 is the octane rating. Octane is nothing more than a measure of the fuels ability to resist spark knock. They do not burn at a different rates. 92 does not provide more power. Both have the same BTU output. Neither one burns cleaner. These are all myths that Shell Oil would like you to believe.

CadillacETC1997, I don't know where you are getting your information from but it is wrong. Burn premium if it makes you feel better, but it is NOT neccassary and you WILL NOT damage your engine by using a lower octane rating.

If the knock sensor went bad (very highly unlikely), the engine would ping, not immediately self distruct. You fix the sensor and move on. You are waaay to paranoid and misinformed about this.
To add to this, I suspect the algorithm is designed to err on the side of caution. By that I mean that if the KS does not respond as expected or the KS module fails a PCM test, it probably defaults to the lowest available timing maps (or the 87-or-lower octane timing maps) to avoid the potential for damage in exactly these circumstances. I don't know under what conditions the KS or KS module are tested, how often it happens, etc. That would be good information to have if anybody knows. I'm not going to hold my breath.
 
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