slwhite

My 2002 knocks slightly under WOT with 91 octane gas. Does anyone know what octane level will stop the knocking completely? I have found some 92 octane but have not tried it yet.

jnjboc

I have used Sunoco or Chevron 94 since I brought mine home, and it screams like a banshee under WOT. Never a knock at all. Some will say it's overkill, but I don't mind paying an extra buck for a fillup...

Andy64

I suspect the answer may not just be a straight octane number. You may also have to figure in gas quality and potentially some deposits in your fuel delivery system. I would definitely go for the 92. I would also try some Chevron/Techron cleaner if your gas is from companies that do not use cleaning additives in their gas. Not sure what is in your area but exxon carries 93 around these parts in the Northeast and I tend to stick with them and have not had any knocking problems so far.

barondw

Shouldn't the computer retard timing if it sense knocking? And I so it doesn't matter what level of octane is used.

Thus if there is knocking does that mean that engine management is doing its job?

slwhite

I should have clarified. It knocks momentarily and then goes away. I assume the engine controller has detected knock and then compensated. But when this happens, I am sure I am losing some power due to retarded timing. I want a sufficient octane level to ensure that this does not happen.

TheDVS1

I have to run an Octane Booster in my old Firebird to keep that puppy happy. I've been using the NOS brand booster lately in the 'bird, and it seems to work as advertised. At Autozone it's about 7 bucks a bottle for up to 3 point boost, and around 9 bucks for up to 5 points of octane enhancement. The car will not diesel when I run the NOS booster, which also has a lead-substitute/lubricant for my valve seats. I might try a bottle in the Z just to see what happens too. I believe it's safe for cataclysmic converters, but it's probably a good idea to read the label before purchase.

Keep in mind that there are many manufacturers of booster, but I prefer NOS so far.

barondw

I would use increase the level of octane, assuming youhave a choice, one level at a time until the knocking goes away.

If this is not an option then try octane boosters.

ZO6Les

I would go with 93 Octane, but first as someone else suggested run a bottle of Chevron Techron Fuel System Cleaner through the car. You may have some carbon build-up that is making the fuel burn less efficient. I believe 91 is the highest you can get in California, and people drive there all the time with no knock. Also get a fellow Vette enthusiast in your area to ride with you, what you are hearing could be a lot of things OTHER than knock.

Les

AU N EGL

Does Iowa still have the corn alcohol blended fuels?? 10% alcohol ?

Scott03Z06

You do realize that a point is a 0.1 increase in octane, right? Pretty expensive for a very small gain in octane.

May want to look into getting some toluene and use as your octane booster. Probably a lot cheaper too.

slwhite

Yes, but I do not use it. Only pure gasoline.

Z.06

My 2001 Z06 also knocks on 91 octane. It did this on a long trip through Texas, NM, AZ, CA, NV, UT, CO this summer. Mine will knock at part and full throttle. Probably the worst was the 91 octane crap gas in California. As soon as I got back to the 93 octane (R+M/2) stuff in Texas it was fine. I do not know whether 92 octane will satisfy it or not.

I had it into a dealer in Grand Junction, Colorado and he pronounced the car fine, though he did admit it has ignition knock. Put it into the dealer in Houston after the trip and he claimed the engine was knocking because of carbon deposits. He wanted to charge $250 to run a can of GM top end cleaner through the engine to decarbonize it. He said he had complete faith in his tech and offered the job for free if he could not solve the problem.

Well the job was free. He even reflashed the latest updates in the ecu, to no avail.

I have a buddy with a 2003 Z06 in Los Gatos, CA, and he runs the 91 octane crap gas with no clatter. Why can't GM fix all the cars to run that way?

Marine

I use Cali 91 crap gas. I get bad knocks when I let off the gas. Like pulling to a stop at a light.

PowerMad

On the trip home from the NCM, I was unable to find 93 Octane in some states. However, since getting back to Houston, my baby has been on 93 Octane, low sulfur, brand name gas. It does not knock.

hope that helps,

dave

mountainbiker2

With 91 Octane I have to add about 16 ounces of Torco for a 10-12 gal. fill-up. Works fine for now.

Lensboard

Wow, after reading this thread I understand what my car is doing. I have an A4 01, and it knocks at mid accel. Now I understand what it is doing. Well the good news is that I just sold it, and have a 500 mile 03 MY z06 on a truck coming at me from illinois to california, looks christmas will come early this year !!