How many catalytic converters on my car and will replacing with o2 sensor improve MPG?

2005 FORD FIVE HUNDRED
120,000 MILES
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DAVENOOB
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I have a pre 03/04 five hundred just realized this makes a difference. Anyways my gas mileage is shit but with ac. I recently changed the 2 catalytic converters and o2 on another car gas mileage increased 25%. The replacement converters were significantly smaller than originals.

Can this help with my 20 yr old car? Also I keep finding it has 1 or 3 catalytic converters.can you help with this also? It's awd se
Jul 12, 2025 at 3:22 PM
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MECHTRIX
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Yes i believe yours has 3 cats ..and yes... if any of them are bad and you replace them you should see a gain in mialage and most likely a few other changes too"..that said " it varies from car to car and by different models but somtimes it can be pretty significant and of course depending on how bad your fuel problem is to begin with.but more importantly a new cat will couse all the engine mangement sensors and other various components to re calibrate and it should change the whole way it runs and will definately improve regardless.. best of luck
Jul 12, 2025 at 10:07 PM