hi. do U have digital engine management and/or gamijectors? if so, U could fly lop.
if not, fly always peak tit around 1650 f. for long distance (2_5h) i fly 30 inHg, = approc. 70%hp.
for short flights (1-2h) i fly 27-29 in Hg
at all altitudes.
i consider this efficient/economical. the gain of speed at map >32 in Hg is not worth the fuel consumption, shorter travel time nor engine wear. considering different wind speeds/directions at different altitudes optimises travel time/ fuel consumption. my longest regular distances flown weekly were scotland and northern spain. goint to higher teens (fl160+) for speed efficiency is worth only for trips longer than 3 hrs. (time+fuel for climb vs. speed gain at levels).