1999 Durango 5.2l p0138

I have a 5.2L 99 Durango with 145k on it. The CEL light came on so i stopped by the auto store to pull the code, which was p0138, bank 1 sensor 2. Figured i needed an O2 sensor but had to wait for payday. I filled the tank the next day, drove another 5o miles and hte light shutoff. It hasn't came on since.

I figure it is fine, but I am wondering if i am getting the best MPG out of it. The computer in the truck says 12.9. I swear it use to get 14+mpg, but that was when my wife drove it.

What should i expect for MPG out of this PIG?

it's off because it's likely on it's way out, change them out with good quality replacements and your mileage should improve

I was told it is best to replace them all and at the same time. Any idea on how man o2 sensors it has? The light has come back on for over 2 weeks, but still the MPG is at 12.9.

nope no idea without getting under the hood, 2 at least likely! crawl under and check or take the vin # to the dealer and they'll hook you up