Race fuel
Le Mans Master
Joined: Oct 2007
Posts: 9,660
Likes: 3,360
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Wasn't by choice really. I went to the track with a little less than I should have. In order to make it home I put two gallons in. Now I'm getting a Code 430 on bank 2 low efficiency. Guess I'm going to have to buy a cat. 
Team Owner
Joined: Aug 2005
Posts: 34,988
Likes: 515
From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
2018 Corvette of Year Finalist
2017 C4 of Year
2016 C7 of Year Finalist
St. Jude Donor '09 thru '20
You were low in gas and put 2 gal of race fuel in the vette. I'm no expert but, the C5 owners I know with S/C mix 5 gal of race fuel then fill up with regular gas.
PM sent
PM sent
Pro
Joined: Feb 2006
Posts: 543
Likes: 0
From: powhatan va.
just take the cats off and knock the honeycombs out and reinstall them, i did mine and it flows much better. if you have pollution restictions in your state then you are SOL you will have to get one.
Race Director
Joined: Jun 2004
Posts: 13,922
Likes: 700
From: WI
I'm not sure all what that codes means, maybe just the O2 got gummed up? O2's do not like lead either. I highly doubt your cat is damaged from just that. I've seen O2's cleaned with a torch but if it's old I'd just replace it.
Instructor
Joined: Jul 2009
Posts: 216
Likes: 0
I dont think 2 gal would have killed your cats mixed with 91 but it might have damaged your o2 sensors. I used half Trick 101 half 91 everyday with my 350z. The leaded gas will kill your cats and o2 sensors. Trick 101 is unleaded too. Higher octain fuel burns cooler and helps prevent detonation. Usually only beneficial when tuned for it, for FI or high compression motors.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Dilute it with 87 octane unleaded
A couple of summers ago when we had a gasoline shortage here in Charlotte I was almost out of gas and could not find anything but race fuel. Sooooo, I put 3-4 gals in so I could get home.
Check engine light went on immediately and the car ran like s**t; temps also went up. The car had much reduced power. I soon found some 87 octane unleaded and filled the tank. The check engine light went out and the car ran like normal. I subsequently changed out the O2 sensor just in case. Since then (2 years later) the car and cat seem to be fine.
For what its worth.
Check engine light went on immediately and the car ran like s**t; temps also went up. The car had much reduced power. I soon found some 87 octane unleaded and filled the tank. The check engine light went out and the car ran like normal. I subsequently changed out the O2 sensor just in case. Since then (2 years later) the car and cat seem to be fine.
For what its worth.
Team Owner
Joined: Dec 2007
Posts: 20,974
Likes: 261
I have a buddy with (not bragging for him) making a point
2 saleens
GN turbo
TA turbo
ETC. he does not have emmissions to pass, he has always run 110 in them, and the CATS are totally ruined from it.
The reason I mentioned some of his cars, is that it happened to all makes and models he has. Iwould not reccomend it alot if you have to pass, or buy the SS Straights for racing, and put the cats back on when needed.
I personally used to mix it in my 5.0's, and I liked how they ran, they were not totally stock though.
2 saleens
GN turbo
TA turbo
ETC. he does not have emmissions to pass, he has always run 110 in them, and the CATS are totally ruined from it.
The reason I mentioned some of his cars, is that it happened to all makes and models he has. Iwould not reccomend it alot if you have to pass, or buy the SS Straights for racing, and put the cats back on when needed.
I personally used to mix it in my 5.0's, and I liked how they ran, they were not totally stock though.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
A couple of summers ago when we had a gasoline shortage here in Charlotte I was almost out of gas and could not find anything but race fuel. Sooooo, I put 3-4 gals in so I could get home.
Check engine light went on immediately and the car ran like s**t; temps also went up. The car had much reduced power. I soon found some 87 octane unleaded and filled the tank. The check engine light went out and the car ran like normal. I subsequently changed out the O2 sensor just in case. Since then (2 years later) the car and cat seem to be fine.
For what its worth.
Check engine light went on immediately and the car ran like s**t; temps also went up. The car had much reduced power. I soon found some 87 octane unleaded and filled the tank. The check engine light went out and the car ran like normal. I subsequently changed out the O2 sensor just in case. Since then (2 years later) the car and cat seem to be fine.
For what its worth.
I filled the tank and got rid of the code. So far so good.
That's on the back burner for now as I'm starting a cam swap this weekend. I'll deal with it if it pops up again.
Thanks for all the input guys!
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
Only the 96 "tells the ECU if the Cats are working."That is the function of the post cat sensors.
On all C4s, the pre cat O2s are used by the ECM/PCM to adjust the air/fuel mixture.
That is why you likely will not know on a pre 96 if the cats are working or not.
The OP is getting an OBDII code from the post cat O2s that shows one or more is not doing it's job.
On all C4s, the pre cat O2s are used by the ECM/PCM to adjust the air/fuel mixture.
That is why you likely will not know on a pre 96 if the cats are working or not.
The OP is getting an OBDII code from the post cat O2s that shows one or more is not doing it's job.
