I took the data and visualized it.
If the information was too incomplete it was ignored.
If an MPG was rated "x to y MPG" or if the MPG was given in city and highway driving the value in use is (x+y)/2.
If the MPG is listed in different speeds an average is calculated or the MPG closest to 65 mph is used.
There are a lot of different engines swapped into vanagons and they are taken into account.
MPG is Miles per Gallon, which is opposite compared to l/100 km. When using MPG a higher value is better.
To get a l/100 km-value out of an MPG, divide the value with 235.22 (235.22/25 mpg = 9.41 l/100 km).