I just had someone in from the oil co to give me some additional info.
My burner is running at 78.5-80% efficiency. I probably don't need to
upgrade the burner right now. Even he admitted that, although the
furnace is in good condition, it is using much more oil than it
probably should. Replacing the furnace w/ an internal water heater is
about $5000 and a furnace with an indirect unit is about $6800. Both
numbers are tough to swallow this year. The alternative is to cap the
lines to the tankless and install a gas Water heater. According to the
gas co, it should cost about $50/ mo to run the HW. On the other hand,
according to the oil co, based on a 1200 gal consumpsion, probably 250
gal is HW. so now we are only talking about the difference of $600/yr
for gas vs $750/yr for oil. On top of that, it will cost about $700 to
install the new heater and cap off the tankless. Then, as a friend of
mine reminded me, if the cost of gas continues to rise, the $150/yr
difference disappears since the oil is capped at that price.