I keep track of my mileage, very closely, as a check on how my vehicle's
condition is.  Over the past 3 weeks, and 7 fills, I averaged 23.75 mpg.
Highway, freeway and mountain driving, mixed.  1.8 liter "Mouse motor" from
a 92 VW Cabriolet, hooked through a diesel vw 5sp manual tranny and turning
14" 185 Nankang tires.  Interestingly, I seem to do better in mountain
driving, making me believe that  moving weight and mass is not as
influential on miles per gallon as moving frontal area down the interstate
at around 75mph, like I normally drive.
  I did notice, according to my past mile per gallon records, that when I
added the furniture and tankage to my formerly passenger van, my mileage
decreased from about 25.75...
  Don Hanson