Should you change the 02 sensors or just wait till I get an engine code? It's my 2004 f350 5.4 with 151k, I only have two sensors one on each bank. Dealer just told me to keep them until the truck throws a code or engine light and they want 62 a peice!

 

Listen to the dealer, they're being honest with you about the sensors.

 

I could have sworn I read in a thread on this site a while back to change them out so you gain performance and MPG?

 

That would happen only if the current sensors have actually degraded to the point where those operating attributes ("performance" and fuel economy) have been negatively affected. If you cannot prove that they've been already adversely affected, you're simply guessing and your results from new sensors will be whatever they will be, whether that means no change, a little change, or a big change.

It's your money, do whatever you want in the absence of factual data. Beware though, the "butt dyno" is not accurate, it's going to tell you what you want to hear, especially after shelling out cash. And, if you start tracking MPG only after you make a change, you WILL change your driving behavior unconsciously, usually enough so that that change in behavior is is enough to change the results of the calculations. It's a bit of a testing bias issue and is a part of human nature.

 

I feel my truck is the same in power as it was right after I had the 4.30 gears installed. And now that winter is here I'm hanging around 9mpg which is normal I suppose. I don't know nor remember what the truck did when I bought it new so maybe it was 11MPG during the winter months I can't say