Minimum octane that safe for car?
Team Owner
Joined: Mar 2001
Posts: 21,325
Likes: 3,841
From: small town in S.E Pa. PA
St. Jude Donor '03-'04
People have trouble running 91 octane...but in a pinch, when all you have is 89 it will make your car move, but at a cost of reduced performance, but it will get you home.
Team Owner
Joined: Apr 2000
Posts: 27,818
Likes: 8
From: CT
You can run the lower octane...but I wouldn't lean on the loud pedal too much.
Like the above mentioned, it could ping. Some have trouble keeping the motors from detonating with 91 let alone 89. It's hit or miss though.
Like the above mentioned, it could ping. Some have trouble keeping the motors from detonating with 91 let alone 89. It's hit or miss though.
Pro
Joined: Jun 2005
Posts: 593
Likes: 1
Originally Posted by bornagainvetteaddict
I read in the manuel that medium grade (89 octane) is ok with the car. Has this been your experience?
The PCM's knock learn will readjust so if ping happens it will protect engine by backing timing off so you can use the 89 if you need to
Melting Slicks
Joined: May 2003
Posts: 2,840
Likes: 301
From: Bonita CA
You won't save money if that is your objective because when the timing retards to compensate, you will lose mileage. You can't get something for nothing here. If you want to run regular, sell the Vette and buy a Toyota.
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Burning Brakes
Joined: May 2002
Posts: 831
Likes: 0
From: Albuquerque NM
91 is the highest we can get at a "normal" pump. It's 23 miles to where I work, one way, takes nearly an hour mixed city/freeway & I've been getting right at 22mpg, DIC usually shows 22.8 or 23.
Melting Slicks
Joined: Dec 2003
Posts: 2,340
Likes: 722
From: Chicago N/W Suburbs
I have experimented with 3 consecutive tanks of 87 octane, and have compared it to regular use of 91 octane. Here are my results.
For Reference.......
- 2001 Corvette Convertible with Automatic & 2.73 axle ratio
- commuting only, no performance driving
- 25 to 50 mph driving speed with 8 minutes of bumper to bumper traffic on average, and around 20 traffic lights, traveling an average distance of 17 miles and driving time of 40 minutes per trip.
Results off DIC.......
- 91 octane 22.5mpg
- 87 octane 21.5mpg (5% loss in gas mileage efficiency)
No pinging, but emphasis on "never hard" on the throttle.
Conclusion........
Driving conservatively, 87 seemed fine on the motor. But with the price of gas at $2.50 a gallon for 87 regular and $2.70 for 91 premium, it's "Break-Even".
Buy Premium.
For Reference.......
- 2001 Corvette Convertible with Automatic & 2.73 axle ratio
- commuting only, no performance driving
- 25 to 50 mph driving speed with 8 minutes of bumper to bumper traffic on average, and around 20 traffic lights, traveling an average distance of 17 miles and driving time of 40 minutes per trip.
Results off DIC.......
- 91 octane 22.5mpg
- 87 octane 21.5mpg (5% loss in gas mileage efficiency)
No pinging, but emphasis on "never hard" on the throttle.
Conclusion........
Driving conservatively, 87 seemed fine on the motor. But with the price of gas at $2.50 a gallon for 87 regular and $2.70 for 91 premium, it's "Break-Even".
Buy Premium.
Burning Brakes
Joined: Jul 2003
Posts: 843
Likes: 9
From: Laguna Hills CA
Define "safe".
As many have mentioned, the car will "run" on several grades of gas, including fuels lower than the recommended 91 octane minimum. This is due to 2 key elements that the PCM uses -- the High/Low octane fuel maps, as well as varying knock retard. How effective these things are, ultimately depend on the motor and your driving style. Normally, the PCM is able to sort things out w/o doing too much damage, however that's assuming that a bunch of variables are in your favor.
Personally, I see knock retard and ping when hot w/ 91 octane gas . . . I'm also using shaved heads, a somewhat agressive cam, and slightly advanced timing. KR is only able to take care of so much, which is why I'll end up running something other than 91 when I know that I'll be beating on the car.
So, if we define "safe" as "won't cause irreparable harm" then you'll probably be fine assuming that you don't beat on it. OTOH, if we term "safe" as "won't cause the PCM to go through acrobatics to keep the car running well", then 91 should be the minimum.
As many have mentioned, the car will "run" on several grades of gas, including fuels lower than the recommended 91 octane minimum. This is due to 2 key elements that the PCM uses -- the High/Low octane fuel maps, as well as varying knock retard. How effective these things are, ultimately depend on the motor and your driving style. Normally, the PCM is able to sort things out w/o doing too much damage, however that's assuming that a bunch of variables are in your favor.
Personally, I see knock retard and ping when hot w/ 91 octane gas . . . I'm also using shaved heads, a somewhat agressive cam, and slightly advanced timing. KR is only able to take care of so much, which is why I'll end up running something other than 91 when I know that I'll be beating on the car.
So, if we define "safe" as "won't cause irreparable harm" then you'll probably be fine assuming that you don't beat on it. OTOH, if we term "safe" as "won't cause the PCM to go through acrobatics to keep the car running well", then 91 should be the minimum.
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
Originally Posted by bornagainvetteaddict
I read in the manuel that medium grade (89 octane) is ok with the car. Has this been your experience?
Safety Car
Joined: Oct 2004
Posts: 4,816
Likes: 132
From: Plano TX
In Dallas mid grade (89 octane) is 2.49 a gallon. 93 Octane runs .10 cents more at 2.59 a gallon. So you save a grand total of 2.00 a tank. And if you consider what Ron just posted.. A 5% loss in efficiency or gas mileage on the cheaper stuff. The net result is about a .20 cent savings per tank full!!. If you carefully budget your income. I think you can make room for the premium gasoline. If you cannot afford an extra .20 cents a week I can arrange to send you a check once a month for .80 cents just send me a message...
Le Mans Master
Joined: Dec 2000
Posts: 9,909
Likes: 1,858
From: Hot Springs AR
Originally Posted by bornagainvetteaddict
Saving gas $$$ was the only reason I was wondering. Thats a very interesting point that I will not save any money. What type of millage are you guys getting?
Now, on my '94 Z-28 (LT-1 engine, MN6), I found that I got the best mileage with 89, but even then it was just a small amount. Then as the engine got more miles on it (175K+ as of today), the octane needs slowly crept upwards. I'm thinking it's got some carbon buildup that I'm not going to be able to get rid of other than a full teardown. So she gets 91-93 octane fuel now as well.
HTH, and have a good one,
Mike
Advanced
Joined: Jan 2006
Posts: 65
Likes: 0
From: ADELANTO CA
Gas
I HAVE PEOPLE SAY WHAT KIND OF MILEAGE DO I GET. I GET AROUND 29 TO 30 ON THE HIGHWAY. IN TOWN T GET AROUND 22 TO 24. THEY ALSO SAID LOOK AT THE PRICE YOU PAY FOR GAS. I TELL THEM I PAY ABOUT $2.00 MORE THEN YOU DO,AND LOOK WHAT YOU HAVE TO DRIVE. 
STAY WITH 91 OCTANE.
STAY WITH 91 OCTANE.
Last edited by JACK EPPERSON; Jan 31, 2006 at 10:29 PM.
