My friend and I thought we bought Sunoco 110 unleaded, or so the dealer told us, for the drag strip. However, I'm pretty sure it was leaded now. It left a white residue in the exhaust pipe and on the back of my bumper. I also drove 80 miles home with the 110 octane. When I got back home I filled back to a 1/2 tank with 93. 1/4 mile away from the gas station my CEL came on. I pulled the codes and it was the P0420 cat code. I cleared the code, and drove around for another 40-50 miles without it coming back on. This morning I fill my tank back up with shell 93. About 10 miles from the station my CEL came back on again. So, can a cat (UR Hi-flow) handle a little more than a 1/4 tank of leaded or is my cat cooked? The exhaust still has that strong sweet smell also. I'm also going to run a tank of 93 back through it and clear the code and see if it fixes the problem.

Any ideas?

 

Sounds like your CAT is screwed. Highest octane unleaded I have seen is VP racing "MS 109". It is 109RON 101 MON for an actual AKI octane rating of 105. Bulk price on this fuel (befor tax) is 5.75 a gallon. Leaded race fuel is always cheaper than unleaded so if you paid less than 5.75 a gallon plus tax then you undoubtedly recieved leaded fuel.

Lead also affects your O2 sensor, and they are what is used to determin your CAT's efficiancy. You could need to replace any one (or all three) of the following parts: Front O2 sensor, CAT, or Rear O2 sensor.

Keith

 

Sunoco 110 IS leaded...no doubt. New cat and sensors....you'll be good.

 

I've seen other posts where 02 sensors can handle a few tanks of lead, they just dont last as long. I'll put my stock cat back on and see what that does.

Another friend of mine ran the same fuel with a hi-flow cat but his CEL never came on, and he said the race gas smell is already gone. Strange.

 

Hi

We used to be a Unocal race gas dealer, so we would always run our cars with leaded & unleaded high-octane gas.

Basically the 02 sensors should be fine, the leaded gas is definately hard on the sensors, but not too bad. The rear sensors are fairly robost and can take thousands of miles of leaded, the front wb02 sensor is a little bit more sensitive, but in my experience, after a few thousand miles of leaded, only the sensor response tends to slow a bit, the sensors usually still work.

Your cat, however, is probably done...

Hope this helps.

Cheers,

Gary
Gruppe-S

 

Good info Gary, especially since a new front O2 runs $200 and a new rear O2 runs $250!!

 

Hmm, the station back home where Im from by the drag strip has a leaded pump but the nozzle is a bigger size, meaning it wouldnt fit in a regular car. I guess this isnt always the case?

 

Well, we bought the gas out of a 55 gallon drum and put it in a 5 gallon container.

Gruppe-s: Do you think my 02 sensors are still acting like new or will they "react slow" on just 5 gallons?

 

My GVR4 I used to run tank after tank of CAM2 leaded 110, never had a o2 problem. Always carried a metal skewer for shiskabobs<sp?> to hold the flapper door on the car open and just line up the bigger nozzle.