it upside down. It will now spray out a cold sub-zero stream of freezing spray (very cold stuff - be careful on skin). Soak the entire O2 nut -- all sides, they give it a try. Worked very well on both my O2s (right away). Tried numerious times (w/out spray) on the psngr side using PB blaster, heating, swearing etc. Freezing spray is the trick - I also used a loaner O2 socket set from Autozone.