C5/C6 Octane Usage?

[hub_cap]

There have been discussions as to which fuel to use in C5 and C6 engines. The manual recommends premium (93 octane) fuel. I have tried a tank of 87 octane in my Z06, but now use 93 exclusively regardless of cost difference (brand doesn't matter, except no Citgo in my vehicles).
Several people who have 07 cars say that they have been told that 87 octane is o.k. What do you use in your 5.7 liter or better engine?
I would like a poll that shows:
C5
regular grade (87)-
mid (89)----------
premium (91-93)--

C6
regular grade (87)-
mid (89)----------
premium (91-93)--

[Patrick]

HubCap,
While you can certainly make a poll, I think you'll find that the vast majority of C5 owners (and, I assume C6 owners as well) routinely use the highest available octane when getting gas. So the poll results won't come as a particular surprise.

The better questions to be asked are:
1. Do you add Techron when you fuel up, and if so, how frequently? and
2. Do you use a Top Tier brand of gas?


-Patrick

[6 Shooter]

I always give it the best the gas stations has to offer!

L8TR - D

[04 Commemorative]

Always use premium and try to make it Shell unless desperate!

[DennisC5]

Originally Posted by 04 Commemorative

Always use premium and try to make it Shell unless desperate!

V-Power!!

then premium Top Tier...

then premium name brand...

[Remo]

I always use 93 octane and Techron three times per season.
Remo

[jrose7004]

91 octane is about all you can find around here.

[Patman]

In order to be assured that you've got no knock retard at all in hot weather, the LS1, LS2, LS6 and LS7 engines most definitely need 94 octane. You're fooling yourself if you think these engines can run on 91 octane in 90 degree weather and not have some timing pulled out by the computer. Under conditions like that you're probably seeing 2-3 degrees of knock retard if not more.

I run nothing but 94 octane in mine.

[6 Shooter]

Originally Posted by Patman

I run nothing but 94 octane in mine.

I've ran 91 without any problems.

[Patman]

Originally Posted by 6 Shooter

I've ran 91 without any problems.

I'm sure you have run it and not had any actual problems with it, but I can tell you without a doubt that your computer is pulling out timing when it's hot outside. It simply is not possible for an LSx engine to run 91 octane in hot weather and have zero knock retard. Hook up a scan tool and you'll know I'm telling the truth. GM's spark curve is too agressive to run 91 octane in hot weather. You will get away with no knock retard in the lower gears, but once you hit 3rd gear it will start pulling out timing. You might not notice it, but when it's pulling out timing, you are losing horsepower.

[70s_Muscle]

As much as possible, I try to run Sunoco GT100 in my 2006 Z06. If I'm doing a lot of driving I will blend 93 octane premium (50%) with 100 octane GT100 (50%) for an effective octane rating of 96.5. You can change the percentage to raise or lower you octane rating and/or cost.

[Victory Red C6]

Only PREMIUM for my C6. In most place that I have seen premium is about $0.20 more per gallon over regular unleaded and $0.10 more per gallon over mid grade. If the 18 gallon tank on your C6 is completely dry that comes to $3.60 more for a tank of premium over regular unleaded and only $1.80 more vs mid grade.

Since owning my Vette I have kept a record of every gallonof gas purchased assuming the 10 cent and 20 cent difference as mention above, it has cost me a mere $21.93 or $41.34 respectively. Total gallons purchased 254.021 at an average price of $2.766 per gallon.

To me the potential for decreased performance is worth the savings, or even worse ruining an LS2 and being without my Vette when the engine is being rebuilt or replaced.

By the way I am averaging 23.8 miles per gallon

If someone is trying save a couple of bucks on a tank of gas they should probably look for a prius or some other hybred. Well, I guess all of you buying less than premium makes it a bit cheaper for the rest of us using premium. Just me 2 cents premium cents that is.

[Evolution1980]

I'd venture a guess that across pretty much all years of Corvettes, we run the higher/highest octane we can get our hands on. Especially in the older, non-computer'ed high compression engines. Higher octane = lower flash point = cooler burning combustion.

I can not speak from experience as I've never out anything but 92 or higher in my car. But I'd agree with Patman, especially with the newer cars. The computer will compensate enough that the driver without third-party monitoring will likely never know the engine is being retarded. (hahah..."engine being retarded" for once it's not the driver).
On the older cars, higher compression engines like my ZZ4 would most likely notice some excessive predetonation from the lower octane. But like I said...I haven't tried it. The cost savings isn't worth the piece of mind I get.

I can say this though...a year or two ago Car And Driver did a shootout with the supertuners and they all ran 100 octane with no problems. So anything more than that is probably overkill.

If I'm not mistaken, it all mostly boils down to the compression ratio of the engine. If it's a low compression engine, lower octane should more or less suffice. Just don't ask me to say what "lower compression" is. (Maybe 8.5:1 or less?)

[Remo]

Originally Posted by Patman

I run nothing but 94 octane in mine.

How nice. But you won't be doing that too much longer.
Remo

[Hotwing]

(brand doesn't matter, except no Citgo in my vehicles). Hub Cap why no Citgo???
He's probably POed at Hugo Chavez