same way my dad gets 57-59mpg highway in his.
mine is auto and it gets 37-41 city, 52 ish highway, best ever was 56mpg.
i ran heating oil, off road fuel, ulsd, but never tried bioD, never cared to, i just put half a quart of power service in the tdi the last fill up plus the off road fuel to see if im getting any improvement…
next tank im gonna add a bit of 2stroke oil to see if that’ll get the mpg up.
as for difference between offroad and on road
offroad is red, 500ppm sulfur, more lubricidity.
onroad is blueish, 50ppm of sulfur, less lubricidity.
i reallly need to find a white 2dr 5mt golf … ;(