use of leaded gasoline hasn't presented any problem for my O2 sensors. I've got about 120,00 miles on them with about 50 visits to the drag strip over the last 6 years, always using some or all leaded fuel (usually about 2 gallons per trip). But it's my understanding that frequent use (whatever frequent equals) will fowl (we've now got birds along with the cats and dogs) the O2 sensors. Take care, Mark