Keep it in Gear, TPS closes shutting off gas flow while the engine adds gas to idle.
BTW, my Performance Package with 19 inch wheels, 3.31 gears and Manual trans has been getting 26 MPG over the last 51,000 miles going by Fuelly, last 10 tanks is 26.1 with the best at 32 MPG and Ford did not get it Calibrated for that because mine is from 1/2 to 2 MPG off on almost every tank. That is also fuelling up at the same gas station and using the same pump so the car is sitting at the same angle when filling most of the time.
Low pressure on your tires allows more flexing, thus causing more heat meaning more prone to tire failure and more wear. That was most of the Explorer tire problems in the 1990's, Ford recommended 25 PSI, less than 50% of the Max pressure on those. My Door tag says 35 PSI but I am running 39f/37r on mine, seems the best compromise between wear, fuel mileage and handling in the corners.
2013 V6 MCoA, Performance Package, Security Package, Comfort Package and Electronic Package.
Mods OEM Backup Camera, BBK Shorties, FRPP Cut and Clamp X-Pipe, Borla Touring A/B's, Airaid CAI, Axle Xchange 2 piece aluminum Driveshaft, Koni Sport Shocks and Struts, Vogtland V6 Leveling springs, Ford Racing 302s wheels wrapped with Continental 275/40 19's, JBL GTO 8628 6X8 in all 4 corners. 2013 F 150 FX2 With a 6.2 Boss