[lsllc]

Yes, I switched from an oil burner (#2 heating oil) to a high efficiency natural gas boiler. The other key ingredient is that the oil boiler was 20 years old and did not have "cold start" (so it always keeps itself at temp even in the summer).

Any modern boiler (gas or oil) will almost certainly be cold start, so it only fires when there's a call for heat. This alone probably saves a gallon of oil a day at least.