If this is what I think it is, it is a material that changes color with
temperature.  When the tank is in use, the liquid in the bottom of the tank
is warmer than the gas space above it.  The gas space is cold due to the
evaporation of the liquid propane as the gas is used.  More flow, more
evaporation, more cooling.

You frequently see heavy-use propane tanks that are cold and condensing
water on the outside due to this effect.  It is most likely that our vans'
tanks do not flow enough to cause the very cold gas area above the liquid.
So, not enough temp difference to indicate the liquid level.

Tom Salicos

> >-----Original Message-----
> >From: Vanagon Mailing List
> >[mailto:vanagon@gerry.vanagon.com] On Behalf Of Troy
> >Sent: Thursday, January 18, 2007 3:35 PM
> >To: vanagon@GERRY.VANAGON.COM
> >Subject: Gauging propane level
> >
> >On the topic of propane level gauges, has anyone tried one of these?
> >
> >
> >http://www.campingworld.com/browse/skus/index.cfm/Outdoor-and
-RV-Accessories/Maintaining-Your-RV/Propane/GLI-Gas-Level->
>Indicator/deptID=3:subOf=14:skunum=4317:src=TSC
> >
> >Best,
> >
> >Troy
> >
> >