I've said it before but I'm not afraid to admit I'm a gas mileage freak.  My 
84 got 24 on the highway and 19 in the city.  I'm kind of disappointed as my 
"new" 83.5 w/c Westfalia gets 23 hwy and only 17 city (well I'm calling "City" 
when I drive over the mountains in 2nd gear to get to work).  I use the taller 
tires, platinum plugs (made a big difference) and I'm really light-footed on 
the gas.  ( I eat brakes and suspension parts for lunch though). I change the 
plugs and distributor every 5000 miles.  I know this is extreme over-kill but 
the I'm no mechanic but the Vanagon seems to be happiest and the gas mileage 
is best when the van is running it's best. 

Bryan