I would suggest some gas preservative based on my recent experiences with old
gas. When I was storing my 164 for 6 months to a year at a time, the only
preservative I could get was for lawnmowers. I'd use about 3 bottles and fill
the tank right up to the snout so there was as little air exposure as possible.
Seemed to work OK. Sometimes the car was a little reluctant but it always
started fairly quickly. If you are in a very damp area you might want to
find a way to block your clutch disengaged so the clutch plate doesn't rust
to the flywheel. (This is not a difficult problem but the "lurch" method of
recovery is a little traumatic and the alternatives are difficult and time-
consuming.)

If it is going to be a LOOOOOOONG, loooong time, you might want to put it up
on blocks. I would also change the oil about 10 miles before you store it so
you have fresh oil throughout the engine. Drive it like you hate it just
before you change the oil so you drain out all the crud you stirred up.

Fresh anti-freeze is also a good idea so you are not trusting in depleted
corrosion inhibitors. If you are in a damp area and you store the car in
the dark, you might want to think about some anti-mildew spray. A dilute
solution of Consan or Physan (normally for garden use) might work in this.

When we went on leave from Panama we'd be gone about 6 weeks or so at a time
and the car(s) we left in the carport ALWAYS got mildew on the upholstery
even when we left massive quantities of desiccant in the car. The cars we
left out in the sun NEVER mildewed, not even in rainy season. They were closed
up tight and when the temp got up to 150-170° inside the car, the resulting
drop in RH (as well as the heat) really inhibited fungal growth. Mildew
likes cool and dark. Of course in the sun is harder on the paint and UV-
sensitive upholstery and plastic parts (rearview mirror, etc).
--
George Downs, Bartlesville, Oklahoma, Central US