First off, I want to say how much I look forward to checking my email. I
appreciate the useful things I've learned in monitoring the list re my 85
Vanagon GL.  I've encountered a problem this last week with my gas
mileage.
1) I monitor it on a weekly basis and was receiving between 17.5 and 19
mpg constantly. The last two weeks my mpg has plummeted to 12-13.
I know its time for a tune up but it shouldn't have dropped so quickly
and dramatically or am I mistaken.

2) What are the steps to a tune up and what should I replace? Is there
anything I'm missing that you all can suggest?

Thanks in advance,

George, Trish & the five monkeys
85 Vanagon GL