OK, I've picked up a spray can of dry graphite lube from Home Depot for about $10.

The label says it is good for extreme temperatures, -73 C to +538 C !

I checked out other types of sprayable lube while I was there, like silicone and WD40, but these don't seem to give out an effective temperature range.

So looks like the graphite lube is the one to use. And like page62 says, this can will probably last me 25 years too !

Thanks again guys for all advice given.