I'm getting about 11mpg (city) in my '99 4.0L AT/242 3.55 with 31's.
I was thinking I would replace the O2 sensor to see if the would help any. My question is should I replace both the up-stream and down-stream or just the up-stream? My thinking is the down-stream is just for the cat, but that is pure speculation.
I was thinking I would replace the O2 sensor to see if the would help any. My question is should I replace both the up-stream and down-stream or just the up-stream? My thinking is the down-stream is just for the cat, but that is pure speculation.