I'm at 77,000 on my '98 F-150 4.6 & figure it's time to change the 2 upstream o2 sensors. Any experiences where I might find the best price? Also am I correct at assuming these need replacing?

 

Motorcraft or Bosch. Bosch manufactures them for ford I believe. Standard Ignition or any other company have unreliable results in the 4.6. They pull intermittent error codes, as I learned the hard way. Don't forget the anti sieze and a little electolytic in the plug. and you'll be ok.

 

I've bought two sets, and both times it's been the down stream sensors that have failed. I have gotten bosch both times. the one for the right side w/ the shorter wires on it was 43.99 and the one for the left w/ longer wires was like 48.99. This was at Advance Auto Parts......

 

I just priced an upstream Bosch from Murray's for $45 today.

 

Changed my oxygen sensor on saturday . I have read several post advising to use Bosch part# 15718, for passanger & 15717 driver's side. I found that on my 98 4.6 part# 15716 worked the best because the othe wiring harnesess were to long 15716 was just perfect for both side, plus it was the cheapest at Napa $42.99