2012 Kia Optima, poor MPG
I had an oild change at Walmart a while back
and ever since then my MPG has been below
25 hwy and around 21 city. I used to get up to
28 sometimes, not sure what happened. Now
it turned off on me yesterday while pulling out
of a parking spot. Checked the code it gave
and said that Oxygen Bank 1 Sensor 2 high
voltage. P0138. I feel like this will fix it but I
need to know if this is the upstream piece or
downstream. Both are not cheap and in 2
different locations apparently but no one
knows which one is Bank 1 sensor 2.