Don't know much about milage, but my 83.5 Van gets about the same that you
got.  I had the same problem with my idle speed jumping up and down like
yours.  It turned out to be two problems, I had a small vacuume leake on the
hose in front of the engine and the idle speed was set a little too high,
100 rpm.  The engine has a high speed idle cutout and when the engine runs
at 1200 rpm (could be 1400, going from memory) the engine is automatically
idled back.  Now because of the two problems that I just mentioned, when my
engine got hot, not just warm, I would have the same problem that you
mentioned.  If you need help setting the idle speed, let me know as it is
rather pickey and has to be done right.

Pete
peterz@gte.net
'83.5 Vanagon

>Just returned from a long trip northern Wisconsin to the Rio Grand and
>back over spring break. Nice place to go birding if there are any westy
>birders out there.
>
>Oh, the VW content... I was surprised to see my mileage vary a great
>deal between over the 3,800 mile trip. High was only 19mpg and the low
>was 13.7mpg. Averaged around 16 mpg. Now we did drive a lot at 65 to 68
>miles per hour and we did run into a good bit of head wind but I figured
>we'd do better than that especially since it's a new engine with only
>6,000 miles on it. Is this normal for an 84 westy automatic?
>
>One other puzzle. Towards the end of the trip I pulled in for gas and
>when I stopped and put the trans in netural the engine began reving up
>and down between 1000 and 1800 rpm. Hasen't done it since so it really
>has me puzzled. Any ideas?
>
>TIA, Bob
>
>84 westy "der bus"