Leaded gas
It also coats the catalyst's & will decrease their efficency as well & the same possibilites of related codes .
I would never put any leaded gas in an EFI closed loop feedback O2'ed car.
They degrade normally with use,add something known to coat the porcelin on the O2's, that is asking for it.
The PCM needs the fast reaction time to properly control fuel.
A coated with whatever O2 will not react as quickly.
It will effect LTFT & STFT.
If it gets slow enough, a poor O2 performance code will result.
If it's a race car who cares but your driver?



