s2k4

On my other Honda, a CRV, recently the Oxygen sensor was replaced due to an engine light coming on. It coded as an O sensor according to the dealer. Ever since the gas mileage has taken a free fall. I brought it back, but since it does not code they won't replace under warranty. Car is carefully maintained, good tire pressure and so on. Besides the O sensor what else could be my problem? Or is it the O sensor? They replaced the front one. They strapped the Computer and it showed good working O sensors.

Any suggestions would be appreciated.

Thanks much.

Arnaud