Have a Professional Look Under the Hood
Your heating system needs to be looked at by a trained technician regularly to keep it running efficiently and safely. Here is some background info to help you look like you know what s/he is talking about.
If your heater is oil-fired, get it tuned up and cleaned every year. Gas-fired systems need cleaning and tuning every other year. Heat pumps are on a 2-3 year schedule. Don't put this off. A regular tune-up will save you on heating costs and extend the life of your heating system, not to mention reducing repair costs. The company selling you oil or gas should have a trained technician who can test your system, clean it and tune it. There are also independent contractors around. It should cost you about $50-100 and will lower your heating bill 3-10 percent.
There are two main drains on heating efficiency: incomplete combustion of whatever fuel you are using and excessively high flue gas temperatures. The results of the technician's tests may show the need for adjustments to your system.
It the technician's best efforts can't get your heater's combustion efficiency up to a minimum of 75 percent, it's probably time to get a new system, especially in these days of rising fuel costs. (For those of you with older burners, you can calculate your annual fuel utilization efficiency, or AFUE, by multiplying the combustion efficiency by 0.85. I don't know why you want to know the AFUE, but I'm told some people do.)
If you have high flue gas temperatures, you are sending money right up the chimney. Average flue temperatures for different types of heaters are: Oil-burners between 400 and 600 degrees Fahrenheit; Oil with flame retention burners between 300 and 500 degrees; gas between 300 and 600 degrees; and a gas condensing system between 100 and 200 degrees.
The technician should also check the carbon dioxide levels. They should be between 10 and 12 percent in an oil burner; between 7 and 9 percent for gas. If the technician is checking oxygen instead, the readings should be 3-6 percent for oil or 5-7 percent for gas systems.
S/he should also check carbon monoxide levels if you have a gas system. The level should be below 1/10th part per million (0.1 ppm).
If there is smoke, combustion is not complete. On a scale of 0 to 10, you don't want your smoke to go above a 1. There shouldn't be any smoke in a gas system.
There are a couple of drafts s/he will check. The overfire draft measured through the combustion chamber should be between 0.01 and 0.02 inches of water on a pressure guage. The breach draft measured through the flue pipe should be between 0.02 and 0.04 inches higher than the overfire draft. (No, I don't really know what any of the means, but let's hope your technician does.) By the way, if you have a sealed combustion or induced draft system, you don't have to worry as much about the drafts.
A technician should clean the burner; (which includes the nozzle, electrodes, and filters), the combustion chamber, heat exchanger surfaces, oil line filter, and flue pipe. On oil systems, s/he will probably replace the nozzles and filters instead of cleaning them.
Boiler and steam lines need their sediment removed. You may need some corrosion inhibitors added to the boiler.
The technician will calibrate your internal thermostat on your furnace or boiler to turn off and on at the right temperatures.
Pumps and fans will be lubricated if they need it.
So you see why you need a trained technician to do this stuff--it's just too complicated for us average Joes or Jos.