Q re two speed furnace fans

Hello,

I know this question has been asked in different forms on this group, but I couldn't find a very clear answer, so I was hoping for some new input.

I just recently bought a Concord 90% efficient gas furnace with a dual speed fan. The fan runs low speed when the furnace is not burning, whereas the high speed kicks in when gas is burned. My two questions are:

2) Does this save on gas (i.e. will the furnace burn less often?), and how many watts is the fan on low-speed?

In my case, the air circulation includes an uninsulated basement, whereas the thermostat is on the main floor.

Thanks in advance, Frenk