Does engine temp have any direct effect on the fuel consumption? Just curious if the computer system in our trucks adjust the fuel output through the injection pump according to engine temperature. I know gassers have this ability.

 

I believe that is the purpose of the IAT sensor, someone with more knowledge will jump in here<br>my 0.02

 

To some degree, it does. If you make short trips around town where your engine temp barely gets to the normal zone before shutoff, your mileage will suffer. Diesel engines operate by heat to ignite the fuel. I am no authority on the relationship, but have seen many posts on other threads that indicate a minor loss of mileage when changing to a cooler thermostat (as an example). I think what what I've seen on this site, 190 - 205* is about optimum operating range. The ECM module takes input from many sensors to determine fueling needs, and adjusts fueling accordingly, which affects mileage.

 

The reason I ask is my 'stat must be open. The gauge will not get above the mark between 140 and 190. This is on a thirty mile trip. I just picked one up. My milage is still low for some reason.