Formulas in graphs

I am trying to get a formula to work in a graph. Here is my graphinfo.xml file. It is not working even after re-adding it to the monitor. However, the headings did change (from oC to oF as I had it to begin with) so I know it is seeing the change ok, it just wont do the formula. All numbers still come out as oC

<CUSTOMGRAPH Name="Ambient Temp">
<YAXISTEXT>Degrees F</YAXISTEXT>
<DISPLAYNAME>Ambient Temp</DISPLAYNAME>
<name>Ambient Temp</name>
<oid>(.1.3.6.1.4.1.318.1.1.2.1.1)*1.8+32</oid>
<type>node</type>
<timeAvg />
<interval>900</interval>
<THRESHOLDENABLED>false</THRESHOLDENABLED>
<FAILURETHRESHOLD>1</FAILURETHRESHOLD>
</CUSTOMGRAPH>