Hi! I have an Excursion limited v10 gas, when I bought it about a year ago the mpg was 11.9 now it is 11.4 almost every 2 months it goes down a decimal.

I changed the plugs, air filter, oil and checked the tire pressure, I'm wondering if it is the oxygen sensor (don't know its location)!



1. What is the mpg suppose to be?

2. What would cause this to happen?

 

Thats not bad for a V 10, from what I hear But Then you will never get great , On that motor ., Maybe you could get them to hook it to the puther so they can see whats its doing, An make sure things are in correct operating range, O2 sensors do get as they call lazy, An that will cause fuel problems , Your O 2 sensors are in the exhaust system, Usually just before the Cat. Converter , an then one after, You Should have one on each bank , left an right sides