Empty oil tank, do I need to refill?

Re: Modern residential gas furnace: ignition Hi, When my Tstat calls for heat, the first part of the cycle for my 21-yr-old Carrier furnace goes like: Open flue damper Start pilot gas flow Spark igniter fires pilot Heat sensor trips gas to main burners etc etc The new Lennox G50 furnace that I'm looking at sez "SureLight Igniter - Made of Silicon Nitride ..." Do the new ones work pretty much like the old ones? If not, brief description of operation much appreciated. Anything on the Lennox also most welcome. Thanks, Puddin'

Due to a problem with asbestos i replaced ALL the duct system in the old house.[forced air oil furnace] The original ductwork was 5 6'' round ducts for the main and second floor and 3 5'' round for the basement. Cold retun was lined joists 8'' with a center to center distance 18'' to 12 '' in diferent places [ 2 floor grates 20''x 12 ]and one 6'' round at the bottom of the stairs I did not install new ducts in the basement to replace the old ones[30% of the worm air] and the cold air return had to be modified [one of the floor grates is on a 12''x8'' duct connected with two 6'' rounds to the cold air plenum] Everything seems to be working fine ,getting a lot more heat than before but since the capacity of the hot air ducts has been reduced by 30% and return modified im wondering if the furnace can overheat or heat exchanger damage Can a furnace technician check temps and if overheating adjust the burner to produce less BTUs? Other sugestions? Thanks a lot:)