Lincoln 97 Towncar 4.6 L with OBDII code 420 & 430

I am getting OBDII error codes 420 & 430. Any idea what would cause both codes to appear and the same time?

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RickHully opined in

Catalyst System Efficiency Below Threshold (Bank 1 AND 2)
Bad gas at one time... or burns a lotta oil
NOTE TO ALL
You CAN get a bad mix anywhere but it's MUCH less likely to happen if you only use high volume stations and brands
Note that this is alt.autos.ford available directly on google groups or from your ISP
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