Though they're expensive initially, there's a quick payback. One stove can heat 2,000 square feet, and will release only negligible amounts of airborne pollutants and ash. A clock thermostat. Closely woven fabrics add as least a half degree in warmth. Service your furnace.
Oil furnaces require regular maintenance, preferably a cleaning and service once a year.
A service contract is probably a good investment, or take advantage of low off-season rates in the summer. Forced-air heating systems require regular filter cleaning or replacement, and ducts should be checked for air leaks. Radiators should be regularly dusted or vacuumed and, if painted, a flat, preferably black paint radiates heat more efficiently. While buying and installing insulating materials in your walls may cost a few hundred dollars, the load on your furnace can be reduced 20 to 30 percent. Attic floors and top floor ceilings are excellent insulation candidates, and if old insulation is present but less than three inches thick, it may need to be built up further.