Monitor Heater ?

[bigdog]

I'm thinking about the possibilty of installing a 'monitor' heating in my Condo unit, to provide heat to the unit while I am away for extended periods during the cold months.

Currently, the unit has FHW Oil heat, 2-zone system. When I leave unit for several days at a a time, I usuually put both thermostats, at around 58 degrees. However, this seems like a waste of oil, since I am not there! Could I adjust both 'stats' lower, without causing issues?

Would a monitor heater placed on the first floor provide enough heat, to offset what would be used with the existing system ?
Also, do monitor heaters use oil? I hear mostly kerosene being used for these type of appliances, not sure if they can burn oil ?

Last, what is lowest temperature do you think safe, to leave unit unattended ? BTW, when away I leave all floor-level cabinets open around sinks so air can flow through that space, to prevent any freezing.

Thanks,
Bigdog