Terrible fuel mileage. 2007 2500 HD Classic 6.0/L
 

Good day


I'm getting terrible gas mileage on my truck. I'm talking about roughly 6MPG in the city. I recently replaced my Manifold pressure sensor due to a -49F cold snap. I run a Sceptre cold air filter, which I just cleaned. It never was this bad before. No codes are showing currently.


Truck has 127k miles on it.


My Mass Air Flow Rate is 11.85g/s at idle.


O2 Bank 1 sensor 1 = 0.825V

O2 Bank 2 sensor 1 = 0.805V

O2 Bank 2 sensor 2 = 0.435V


I have no idea if those O2 voltages are any good or not, lol.


Plugs and wires are less than 2 years old. Truck seems to run fine. Lots of power, idle seems OK. Engine is super quiet.


What else could I be checking? Thanks