Jeep Grille Block Off MPG Increase

[XCRN]

So I had a significant increase in fuel mileage from 15 to 20mpg in my 2000 Jeep Wrangler with a 5.3 LS. This last tank was on roughly the same split of highway/country/city roads I do every day. The ONLY thing I did different as an experiment was block off 4 of the 7 grill inserts with tape to try and raise the temp since it struggles to get to temp quickly even in the summer with a 195* thermostat. I did not see much change in engine coolant temps except at highway speeds it did get a but hotter, but still at a very safe temp.

Stock sized 31” AT tires and just a .75” lift up front and a 5.3 LS with headers. Also added a bug deflector which really took the wind rush down a lot so I assume it routes air over the flat windshield pretty well. Before this even if I tried really hard for mpgs, I would maybe get 16.5mpg. I went and checked that I filled up all the way and mapped out my drives on this tank to verify the numbers were correct, and they were.

So has anyone seen such an increase with something like this alone?

 

[Bootheel Boy]

Doesn’t fuel injection use the engine temp to help regulate the air mixture? If so running cooler due to the engine not getting up to normal operating temp may have it running richer than it should.

 

[XCRN]

Doesn’t fuel injection use the engine temp to help regulate the air mixture? If so running cooler due to the engine not getting up to normal operating temp may have it running richer than it should.

My understanding is warmer air is better for MPG since colder air is denser and will require more fuel to the mixture to make it stoic AFR. Though it could also be said the loss of power from warmer less dense air can decrease efficiency too. Just not sure which will offset the other the most. I just know when I tried different intake setups, the where it was just a cone filter sitting on the radiator had shown a little less fuel flow than an airbox setup away from the radiator