91 octane vs 93???
Thread Starter
Instructor
Joined: Feb 2009
Posts: 218
Likes: 11
From: Portland Maine
91 octane vs 93???
living up here in maine i can not find 93 octane. ive owned my very stock 98 coupe for 4 years and havent been able to put anything in the tank except for 91. the 2 times i found and ran 93 was on the 2 long distance trips ive taken. one to the assembly plant in kentucky, and one to charleston s.c. obviously i filled up with 93 the whole trip... i just wonder if im doing any damage to the LS1? im sure there has to be 1 or 2 gas stations in southern maine that have 93 but its most likely been sitting in the ground for half a year. not many performance vehicles requiring premium....
should i go 91 and some sort of octane boost?...ive seen them on the shelf at car parts stores. or is that even worse?
should i go 91 and some sort of octane boost?...ive seen them on the shelf at car parts stores. or is that even worse?
Former Vendor
Joined: May 2005
Posts: 3,749
Likes: 4
From: Valencia Ca
If your 98 still has the stock calibration then you are going to see "pinging" - the early cars are notorious for their aggressive timing tables and poor effectiveness of their knock retard.
Octane boosters can work but you need one that raise the numbers by whole points - don't be mislead by the off the shelf stuff as many make claims such as "raises octane 10 numbers" This in effect really means 1.0 octane point as a number to them = .1
Either have the calibration reset to allow trouble free operation with present fuel (best to do) or buy some good octane booster, such a Klotz - leaves no residue and will raise your octane easily to 95.
Charlie
Octane boosters can work but you need one that raise the numbers by whole points - don't be mislead by the off the shelf stuff as many make claims such as "raises octane 10 numbers" This in effect really means 1.0 octane point as a number to them = .1
Either have the calibration reset to allow trouble free operation with present fuel (best to do) or buy some good octane booster, such a Klotz - leaves no residue and will raise your octane easily to 95.
Charlie
living up here in maine i can not find 93 octane. ive owned my very stock 98 coupe for 4 years and havent been able to put anything in the tank except for 91. the 2 times i found and ran 93 was on the 2 long distance trips ive taken. one to the assembly plant in kentucky, and one to charleston s.c. obviously i filled up with 93 the whole trip... i just wonder if im doing any damage to the LS1? im sure there has to be 1 or 2 gas stations in southern maine that have 93 but its most likely been sitting in the ground for half a year. not many performance vehicles requiring premium....
should i go 91 and some sort of octane boost?...ive seen them on the shelf at car parts stores. or is that even worse?
should i go 91 and some sort of octane boost?...ive seen them on the shelf at car parts stores. or is that even worse?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
If your 98 still has the stock calibration then you are going to see "pinging" - the early cars are notorious for their aggressive timing tables and poor effectiveness of their knock retard.
Octane boosters can work but you need one that raise the numbers by whole points - don't be mislead by the off the shelf stuff as many make claims such as "raises octane 10 numbers" This in effect really means 1.0 octane point as a number to them = .1
Either have the calibration reset to allow trouble free operation with present fuel (best to do) or buy some good octane booster, such a Klotz - leaves no residue and will raise your octane easily to 95.
Charlie
Octane boosters can work but you need one that raise the numbers by whole points - don't be mislead by the off the shelf stuff as many make claims such as "raises octane 10 numbers" This in effect really means 1.0 octane point as a number to them = .1
Either have the calibration reset to allow trouble free operation with present fuel (best to do) or buy some good octane booster, such a Klotz - leaves no residue and will raise your octane easily to 95.
Charlie
If you ever have a chance to come down to the Groton CT area, PM me and we can meet up and I will data log your car for you. I have EFI Live. I also frequent Carsile and I will also be at Mr Mojos Crab run. We can meet up at any one of those events!
BC
Burning Brakes
Joined: May 2008
Posts: 1,147
Likes: 1
From: Mohegan Lake New York
A question for Bill Curlee and charlie Williams if one lives in an area such as Don C5no good gas no good tuners nearby but unsure if a tune is needed or if 93 vs 91 octane will help at all could a simple check of gas mileage be of use? My understanding is if you get into "pinging" or "detonation" gas mileage will suffer considerably as timing is pulled back among other things. A tune and or data log is the way to go but if in an area where these tool are unavailable could this method be an effective method to use? Because not only is the tune that the car already has part of the equasion but the driving style of the operator.The reason I pose this question when my work commute went from ten miles to a hundred miles I did not only a miles per gallon test but also how much it cost to travel each mile as I tried middle grade and premimun grade even though they cost more per gallon one car in particular cost less per mile to operate on middle grade which I attributed to the factory tune which might have been a little aggresive for the less expensive gas but the better gas probably kept it out of detation thus delivered better gas milage.Think I'm correct or do you think there is something else I'm missing?
Melting Slicks
Joined: May 1999
Posts: 2,365
Likes: 0
From: Vancouver BC
I thought C5s are meant to run on 91 octane...
I always put in 92 Chevron gas. I've put in the 94 Chevron a few times, but I couldn't notice a difference, so now I'm just using 92. I guess when playing around with the tune, higher octane would come in handy
PS: Octane boost from car parts stores is garbage...
I always put in 92 Chevron gas. I've put in the 94 Chevron a few times, but I couldn't notice a difference, so now I'm just using 92. I guess when playing around with the tune, higher octane would come in handy
PS: Octane boost from car parts stores is garbage...
Last edited by Indy; May 11, 2009 at 12:09 PM.
Melting Slicks
Joined: Feb 2006
Posts: 2,172
Likes: 104
From: Des Moines Iowa
I cannot speak to the timing issues on the early C5's but there are many areas of the country that have nothing higher than 91 octane. My area of the country is one of those and I know there are a lot of earlier C5's out here that run 91 with no problems.................
same here in the mid-west
Racer
Joined: Sep 2005
Posts: 383
Likes: 0
From: Michigan
octane rating is a # givin to the fuel resistance to ignite. The higher the # the greater the resistance. If you aren't getting any "spark knock" then your fine using 91. As someone else said, your driving style will also dictate wether or not 93 is necessary
if your getting "spark knock" whats happening is that the gas is igniting before it's supposed to, so you have your piston coming up on the compression stroke while the gas explodes too soon. The upward moving piston hits the exploding gas and it tries to drives the piston down, which causes your rod bearings to rattle (this is not good) for performance or fuel economy, or the engine. But if your not getting spark knock then buying the higher octane gas is a waste of money.
if your getting "spark knock" whats happening is that the gas is igniting before it's supposed to, so you have your piston coming up on the compression stroke while the gas explodes too soon. The upward moving piston hits the exploding gas and it tries to drives the piston down, which causes your rod bearings to rattle (this is not good) for performance or fuel economy, or the engine. But if your not getting spark knock then buying the higher octane gas is a waste of money.
Last edited by c-5-steve; May 12, 2009 at 08:45 AM.
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Burning Brakes
Joined: May 2008
Posts: 1,147
Likes: 1
From: Mohegan Lake New York
C5Steve you are 100% correct,if using 91 octane and no pinging or detationation you are safe but I think the C5's can take advantage of higher octane whereas you use higher octane the factory computerwill adjust to take advantage of the higher octane but it adjusts gradually50 - 100 miles of driving.I have no idea how large the envelope is if you put in 100 octane racing unleaded you are prob wasting your money ,but I would recommend use it if using nitrious.
