Do low-speed fans on new warm air oil furnaces run all the time?

How do multii-speed fans in new OIL warm air furnaces work. One
webpage said that such a fan might use 200 watts, but the one speed
fan my current furnace has might use 800 watts! That seems amazing.

It also gave the impression that when the furnace calls for the low
speed fan, it's because the fan runs all the time. Is that right?


I'm used to the idea that very few oil furnaces have efficiency 90% or
greater, and that they are very expensive. But if I get a
electronically controlled fan with the furnace, that part of the
furnace is eligible for the Federal Energy Credit, and I presume it's
something I want to have anyhow. But I'd like to know how it works
before I buy one.

Thanks.