Exhaust odors can be caused by a myriad of things. Different additives in the gas being a big one. If this just started as winter approached then that is the likely reason. The gas now would be a winter formulation with different additives than the blend used over the summer and can cause a distinct change in the exhaust odor as those additives burn in the engine and converter.
The other possible reasons for exhaust smell would be oil consumption from normal engine wear. That does not normally smell like burnt eggs though, it smells like burnt oil.
Possibly a failing head gasket, but that does not smell burnt, it smells sweet and usually shows up in more than exhaust odor, misfire and overheating along with coolant loss being the big ones.
If you do not have overheating or coolant loss and the oil level is not dropping fast then I would bet it is just the reformulated gas sold in the winter to reduce pollution.
Thursday, December 15th, 2016 AT 4:19 PM