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Catalytic Convertor Damage?

Will 3 to 5 gallons of 100 ocatane, low lead aviation gasoline (used in an emergency) damage my catalytic convertor?

Yes. It can damage the catalytic converter and the O2 sensor(s).


Did you use this just to get you to the nearest gas station and then fill the tank? If that’s the case and the nearest station was only a few miles away, you should be fine. By the time the aviation fuel is mixed in with 10 or more gallons of the good stuff, al it’ll do is slightly raise the octane rating of the gas you put in. I doubt there’ll be enough lead in the fuel to cause a problem that quickly.

Long term use or repeated use would definitely be unadvisable.

So that means we can ignore the warning on the gas cap, “UNLEADED FUEL ONLY”?


How do you get “So that means we can ignore the warning on the gas cap, “UNLEADED FUEL ONLY”?” out of “Long term use or repeated use would definitely be unadvisable.”?

UNLEADED FUEL ONLY means just that. Even the slightest amount of leaded gasoline used in an unleaded engine can damage the catalytic converter and the oxygen sensor(s).

Even five gallons of leaded gas will damage these components. And it doesn’t matter if you dilute it with unleaded gas. There’s still that amount of lead in the gas. So it’ll just take a little longer before all the gas is burned and the lead goes thru the engine and these components are damaged.

Don’t do it.


I’m in agreement that you should not use leaded gasoline in that vehicle. We had a guy pull up to the shop doors once in a Cadillac El Dorado that was barely moving. He had put leaded gas in that car and we never got around to asking how far he had driven it but the motor was absolutely fried.

When I raised the hood I noted both exhaust manifolds were glowing cherry red and they had gotten so hot that the paint on both sides of the hood was blistered.

Once cooled down a compression test verified the motor was scrap iron. While your odds of going to prison are not very high you should be aware that the monetary fine and prison sentence is pretty stiff if you do get caught.
Considering computer forensics is in vogue you now have a virtual paper trail.

I don’t see how 100LL aviation gasoline can directly damage an engine…Most engines love it…But it CAN quickly destroy a catalytic converter and oxy-sensors…Long term use will eventually plug up a converter, causing engine over-heating and loss of power…

I would suspect 100LL is only used in a dwindling number of older piston engine aircraft…In order to use computer-controlled fuel-injection, which need oxygen sensors, modern piston engines must require unleaded fuel, right?? Anyone??

The most commonly used aviation fuel (excluding Jet fuels) is 100LL , i.e., “low lead”. It is dyed blue and contains a relatively small amount of tetraethyl lead—though the amount is greater than what was contained in many automotive grades of leaded fuel before such fuel was phased out. As of Jan 2010, 100LL has a TEL content of 1.2 to 2 grams TEL[7] per US gallon (0.3–0.5 g/l) and is the most commonly available and used aviation gasoline.

So yes it will harm the Cat in short order as it contain as much or more lead than reg. leaded gas did.

While I’m unable to find any data on how much lead it takes to affect the oxygen sensor or cat converter, if the amount contained in the 3-5 gallons used by the OP were enough I have to believe he/she would have tripped a CEL. Of ourse, he/she did not elaborate.

Long term use, or perhaps a full tank or two, definitely, but 3-5 gallons I doubt it.