grade of fuel for n/a - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-13-2004, 10:47 AM   #11
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Humm...when i first purchased my bonnie the original owner said he only uses 89 or higher because with lower grade fuel there was a pinging....but why if there is no supercharger??
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Old 04-13-2004, 10:56 AM   #12
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87 is fine, 89 if you have some mods.

With my intake, and Premium, milage is much higher, atleast on the freeway. I haven't seen much of a difference in town. But in town, i'm not as light on it.

Whatever you do don't switch, the PCM readjusts for the first 75-100 miles.
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Old 04-13-2004, 11:58 AM   #13
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Quote:
Originally Posted by BonneMeMN
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Whatever you do don't switch, the PCM readjusts for the first 75-100 miles.
Are you saying don't switch gas grades??? if so I put in some 89 yesterday as I was thinking that'* what i need to start using...
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Old 04-13-2004, 12:18 PM   #14
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Quote:
Originally Posted by 95neongirl
Quote:
Originally Posted by BonneMeMN
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Whatever you do don't switch, the PCM readjusts for the first 75-100 miles.
Are you saying don't switch gas grades??? if so I put in some 89 yesterday as I was thinking that'* what i need to start using...
Don't worry your car isn't going to blow up All he is saying is that the computer takes awhile to 'adjust' to any type of different fuel you put in it. Therefore running one tank of 93 when you have run 87 for hte past 2 years isn't going to make much of a difference.

Regardless, stick with 87 unless you hear a knocking sound when you go up a steep hill. Otherwise don't waste your money, the car is not tuned for higher grade gas.
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Old 04-13-2004, 01:07 PM   #15
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Correct, if you went back and fotth between 93 and 89, you'd get horrid milage.
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Old 04-13-2004, 01:41 PM   #16
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Quote:
Originally Posted by CFoote
Regardless, stick with 87 unless you hear a knocking sound when you go up a steep hill. Otherwise don't waste your money, the car is not tuned for higher grade gas.
I bet about 90% of the cars on the road today were designed to run on Regular Grade fuel. But the oil companies advertise that their Premium fuels will deliver more power and clean better. That'* why a lot of people are convinced that they need the more expensive fuel for their cars. Or they will say that "Nothing is too good for my baby!"
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Old 04-13-2004, 05:55 PM   #17
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Quote:
Originally Posted by Ol' Timer
I bet about 90% of the cars on the road today were designed to run on Regular Grade fuel. But the oil companies advertise that their Premium fuels will deliver more power and clean better. That'* why a lot of people are convinced that they need the more expensive fuel for their cars. Or they will say that "Nothing is too good for my baby!"
I agree, and when I was 16 I fell for the trick too! Now I know better....although if these gas prices don't go down I'm going to be asking for 1 octane at the gas station
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Old 04-13-2004, 07:00 PM   #18
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OK.. correct me if I"m wrong.. this are all hear say from other gearheads I've been talkin to.. a lower octane will actually burn hotter ( thus producing more power ) but us */C guys can't run it cause it'* a less control burn causing pre-detonation and higher octane is a slower burn. So in theory if that means if you run lower octane and know you won't get KR then you should produce more power right? And Alcohol powered car.. the Alcohol is their to control heat/cooling affect of Alcohol powered car cause they actually use Nitrous as main source of power.. Now you Chemist.. chime in and let me know whats what and if it'* right or not??
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Old 04-14-2004, 12:53 AM   #19
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I ran 87 for the first 8-9 months I had the car I guess. Was getting pretty lame gas mileage so I switched to 89. I don't remember if that alone helped, but after a bottle of STP Fuel System Cleaner I gained at least 40-45 miles to the tank, in the city. Then after a new O2 sensor, PCV valve, wires, plugs...things were a little better. But I still don't get the best mileage, even on the highway. Car runs fine, accelerates almost perfectly most of the time, idling in P is a little rough for my liking though, and 'shuddery,' and a little less rough at idle while in gear. My lead foot at times I can contribute to my mediocre mileage, but I still don't get what I should be IMO. I still don't think 93 octane would help though. I just added another bottle of the STP stuff, hopefully that will help. It'* been at least 7,000 miles since I used it last.
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Old 04-19-2004, 08:30 PM   #20
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HI, Im new here, and Ive been reading alot of useful info on this site for some time. I generally stay silent, but Ive got to jump in on this one. First, An octane rating of "87" is a minimum value set by the Feds. Now consider the feds goals concerning pollutants, conservation etc, and you will get a pretty good picture of why this value, along with other perameters are there.

What does this "87" value accomplish? In the Old days{ before real time computers}, it FORCED manufacturers to lower standard commpression ratios. Most engines were BIG, and having high commpression ratios wasnt a problem because the fuel of the day could support these engines. REMEMBER, not too long ago when leaded gasoline was available, "regular" was often 93 octane or better. The Gov took the Led out, and with it the abilty to run higher commpression ratios of the day.

Your modern obd 2 or 3 computer will basically allow TIMING changes to run on 87. How? BY RETARDING TIMING UPWARDS TO 20 DEGREES. What does that mean? LESS POWER DEPENDING ON tHE amount of retard. In the old days , if I had a detonation problem on some particular fuel, like all gearheads, you pull over, retard the distributor until it went away.With a mechanical distributor, you are stuck with thjat base timing value until you physically change it. Today, The computor has a "window" of manipulation of base timing.{NOT THE CURVE}. So running 87, The motor will detonate{any motor will} but you dont hear it because the computer magically retarded the base timing as soon as the knock sensor sent its ugly message.

The reverse is true also. Feed it 93, detonation will happen at a relatively later point in the cycle { if at all} and the computer will advance timing until detonation occurs again. this mean more power, cooler combustion chamber temps {to a point}, better vaccum {less detonation while valves are still open}, better mileage to a point. OF course you can have too much Base advance, but the computer wont allow it, and this awful gas of today wont support it . Irun 93 when I can afford it.... Just my 2 cents..
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