I would like to bury my coax for a distance of about 20ft. The location
consist of 6" of crushed decorative rocks over the top of very rocky soil.

I intend to take the LMR-400 coax and push it through a garden hose to add
a layer of protection. However, I am worried that condensation will
quickly fill the airspace of the hose with water and it will either
penetrate the coax outer jacket or interfere with the performance of it in
some unknown negative way.

I can not flood the garden hose with petroleum oil as it will soon eat
through the PVC jacket of the coax or garden hose. Ideally, I would like
to flood the hose with the same stuff they put into underground cables. It
has a honey consistency and is not easily displaced by water. I was hoping
for some type of silicon oil but am unable to find anything similar at the
hardware store.

Anybody have any suggestions?