We have a TempStar Gas Furnace Model Number NUGK075DG06 (867) (769425). I can't find the information on the furnace efficiency for this model. Any ideas or where I can find the information. Its an older furnace so the tempstar site didn't have it listed anywhere I was able to find it. Thanks

If it has a metal flue pipe it is probably 70%
If it has a plastic/PVC pipe for the flue it is 90%

I could not find the model number but it is a good model number.