87 or 89 Octane?
10-27-2011, 10:30 AM
#21
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St. Jude Donor '11-'12-'13-'14
I have never noticed any MPG difference by using lower or higher octane fuel... A did a test with my previous corvette which was normally run on regular and did 3 tank fulls with 93 Octane and got ZERO difference in MPG... I'm currently doing the same with my new 2011 to see if there is any difference on this car... But I'm only on my 2nd tank of premium .. So I can't speak for results..
Not trying to start an argument or anything, but I don't think logging your results after 1 or 2 tanks of 87, then putting in 93, and running a couple tanks will reveal anything useful.
There have been numerous studies on this topic though.
10-27-2011, 02:36 PM
#22
Drifting
The underlying reduction in mileage when lower octane retards the spark to prevent knocking is small, about 5%. But variations in the way gasoline is blended can cause larger variations in mileage from tank to tank. The most obvious of those, which most on the forum are familiar with, is ethanol content. If the low octane batch has minimum ethanol of 5% and the high octane batch has max ethanol of 10%, that extra ethanol will lose more mileage than the octane will gain, and the low octane fuel will give better mileage. Another example of that is source within the refinery of the high octane. If the high octane fuel gets its octane from alkylate and the low octane from reformate, the former is lower density so will contain less energy, so you could get the same sort of result as with the ethanol example. Yet another example is the average boiling point of the gasoline. If the low octane sample happens to be higher than the high octane sample, that too could reverse the mileage effect due to density. So bottom line, on any given few tankfuls, besides the variable of your driving habits, there are variations in gasoline blending which could erase or even reverse the mileage effect of the retarded spark. Over the long haul with those tank to tank blending and driving habits averaged out, trust me when I say there will be about a 5% drop in mileage for low octane fuel. But on any given tank, you may not see it, or as explained above, could even see the reverse. Incidentally, the mileage phenomenon does not work the other way. Using high octane in a car designed for regular will not boost mileage because the spark in the car designed for regular will not advance beyond normal. It only works to reduce mileage when low octane is used in a car designed for high octane.
10-27-2011, 02:45 PM
#23
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LDB ... Great explaination !
10-27-2011, 02:59 PM
#24
Pro
Do you think it's possible to duplicate your exact driving habits, throttle position, outside conditions, and traffic with any type of accuracy?
Not trying to start an argument or anything, but I don't think logging your results after 1 or 2 tanks of 87, then putting in 93, and running a couple tanks will reveal anything useful.
There have been numerous studies on this topic though.
Not trying to start an argument or anything, but I don't think logging your results after 1 or 2 tanks of 87, then putting in 93, and running a couple tanks will reveal anything useful.
There have been numerous studies on this topic though.
its not a scientific study for pete sake... just curious...
For everyday driving i just find premium to be a waste of money.. I certainly never found any noticeable increase in fuel mileage spending more for premium and quite honestly dont notice any performance difference using regular... Now Im sure many will chime in blah, blah, blah... If Im loosing a few HP by using regular, honestly i couldn't care less.. 99% of my driving is certainly not with my foot to the floor...
And please don't use that your driving a $60,000 car line... it's a car.. We run all our family cars on regular even though the Acura's recommend premium... (By the way I ran an Acura store several years ago and one of the engineers at Honda during a conversation on just this, laughed and said if your customers want to save 10% on their fuel cost tell them to run regular, they will NEVER know the difference)... Again, recommended is NOT required... to each there own...
Also, my car has no pet name, it's not a her, it's not my baby, girl, or anything other than a my CAR....
put in premium if you want, mid grade, or regular, they run fine... going to the track or plan on racing on the street.. then premium if your looking pull every pony out of it you can..
10-27-2011, 03:08 PM
#25
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St. Jude Donor '13
Yes, our C6 will run on 87.
But I don't like betting my engine on the knock sensors every day. There are enough other things that can go wrong.
But I don't like betting my engine on the knock sensors every day. There are enough other things that can go wrong.
10-27-2011, 03:57 PM
#29
Safety Car
Well, even running gas as low as 87 octane won't hurt your engine .. and it won't somehow hurt your valvetrain as one member that posted here thought it might .. there is really no reason to use that low of octane in an engine that has 10.7 compresssion ratio like the LS3.
Praise the good Lord above that the engineers thought to use knock sensors in these engines. With the slightest detection of detonation, the ECU will pull back timing, but when it decreases spark timing, it also results in a decease of available HP.
So, if your happy with reduced performance, be my guest .. run that cheap regular grade pump gas in your new Corvette. Won't hurt a thing, but seems a bit silly to me.
Just my opinion .. do what you feel comfortable with.
Praise the good Lord above that the engineers thought to use knock sensors in these engines. With the slightest detection of detonation, the ECU will pull back timing, but when it decreases spark timing, it also results in a decease of available HP.
So, if your happy with reduced performance, be my guest .. run that cheap regular grade pump gas in your new Corvette. Won't hurt a thing, but seems a bit silly to me.
Just my opinion .. do what you feel comfortable with.
100% Excellent response! I only wish we had 92 or 93 in California, stuck with 91 octane.
10-27-2011, 04:23 PM
#32
Team Owner
For the LS3, 91 is recommended, but the engine is designed to run on 87 or 89 without hurting the engine. You will lose a little horsepower and possibly gas mileage when running 87/89 depending on the driving conditions, etc.
For the LS7(Z06) and the LS9(ZR1) the engine is designed to run on 91(GM requirement) and GM recommends that 93 be used. 87 & 89 can be used in an emergency, but GM says not to run the engine hard and put in 91 as soon as possible as the lower octane gas can damage the engine. I point this out in case someone reads these posts and thinks that 87/89 can be used in all C6's without damaging the engine. There are differences between the engines GM installs in the C6.
For the LS7(Z06) and the LS9(ZR1) the engine is designed to run on 91(GM requirement) and GM recommends that 93 be used. 87 & 89 can be used in an emergency, but GM says not to run the engine hard and put in 91 as soon as possible as the lower octane gas can damage the engine. I point this out in case someone reads these posts and thinks that 87/89 can be used in all C6's without damaging the engine. There are differences between the engines GM installs in the C6.
Last edited by JoesC5; 10-27-2011 at 04:29 PM.
10-27-2011, 05:17 PM
#33
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Correct me if I'm wrong, but you're saving a maximum of around $3.00 per fill up by using 87? Doesn't seem significant enough to warrant the switch to me. I'll continue using Premium. 
10-27-2011, 09:09 PM
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St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15- '16-'17-‘18-‘19-'20-'21
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10-27-2011, 09:22 PM
#40
Race Director
I've put about 8k miles on my LS2 since I bought it and have run about half of the tanks on 87 and half on 93. I've seen no difference in mileage and really haven't been able to tell a significant difference in power. I've looked at the timing difference between the low octane and high octance tables and, while it isn't insignificant, it has apparently not made any noticeable difference for my daily driver.