I haven't read through this entire post (this site is not mobile friendly), but have you taped up the main and lower grills? Tape up all the seams (ex: between hood & fenders)? Folded back the mirrors? Antennae delete? Tire pressure to ≈45psi?
I did a similar test with fuel fillup versus milage driven, no scan guage, and got 75.9 or 79.5 on one drive from Albuquerque, Nm to Flagstaff to Prescott, Az (I-40 to I-17 to Hwy69). A lot of coasting and drafting the big rigs when they let me.
Still... Hate that car! Will never go to Germany for vacation!
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-Addicted to Chaos-
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