boubou wrote:
Should I replace the propane furnace with an oil furnace?
would that be very expensive? oil tank in basement and all?

First of all, why? Is the existing furnace out of date or in need of major
repair? Is fuel oil currently cheaper in your area per unit of heat times
efficiency factors of typical oil or propane furnaces? Is it likely to
remain so? If there is a savings to be had how long would it take to
recoup the cost of making the change at your rate of consumption? Will you
be in this home long enough for this to happen? Will an oil furnace have
greater maintenance requirements and how much will that cost?