Toro Snowthrower

I did ask the other day. I have a model 38515. Serial # 280000164. It runs and sounds great. Lots of white smoke from muffler. I let it run 20-40 minutes, think ots getting better but starts smoking again. I opened up the shroud to look. The muffler is bigger than I thought 7"x5" approx. It leans to the bottom of the unit. Towards the bottom there is old stains and fresh oil leaking through where the muffler splits in half. Looks like it's been awhile as there are old stains at the bottom of machine. Question is. Do these mufflers go bad? I think it was produced in 08.