what caused my increased mpg?

[kevinkay]

I did a lot of work all at once and now getting better gas milage, not sure what caused it.

start from the beginning......I constantly got 19.5mpg until I got new tires, went from Micheline "energy" to Micheline "primacy" was told by Micheline they are better performance but will get less gas milage. For past year with new tires getting constantly 18.5 mpg.

Did some maintenance work all in a short period and now getting 20mpg

changed transfer case oil
front and rear differential oil
transmission oil/filter change, went from BMW lifetime to Dexron VI
reset Transmission Adaptation values
oil filter housing gasket
DISA O ring replacement (did it because OFG thread said 'good time to replace".
Slotted/drilled brake rotors and new pads

I do mostly highway driving and pretty routine so mpg is not a fluke.
Overall car feels more "peppy".
I am thinking it was reseting transmission adaptation values or I had an undetected vacuum leak at the DiSA valve?