i'm obviously coming in late on this one, but my packaging tape upper grille block has helped more than i expected. i haven't filled my tank yet to get any accurate number, but my jetta usually gets ~400 miles to a (14 gallon) tank. this is nice because every 1/4 tank interval on the gauge should be about 100 miles on the trip odometer. i taped up the grille about halfway through this tank (~200 mi), and now at the 1/4 mark, i've gained 35 miles over where i would normally be (335 vs. ~300).
