THE THREE TYPES OF HEATING OIL

There are three main grades of heating oil, called No. 2, No. 4, and No. 6.

The first is the cleanest and most expensive; the last is the dirtiest and cheapest; and No. 4 is a mixture of the two. Unless you're installing a new boiler, you don’t get to choose which oil you use; your boiler and burner will be manufactured to burn one. No. 6 is heavy, sluggish and dirty.

Craig Rosenman of New York City's Stuyvesant Oil estimates that No. 6 is about 40 percent less expensive than No. 2 and provides more heat per gallon than any other grade. The downside is that, because it is very dirty, the equipment using it requires more costly maintenance.