I have a 1998 2.2 L Subaru Impreza sport outback and I recently smelled oil burning. I look under the car and there is oil shinyness on the bottom of the car running down to the exhaust which is burning the oil. It looks like it’s leaking from the seal at the bottom of the engine. I touched it and it feels like the gasket is starting to sag. Is this symptom of bad gasket or something else. I checked the oil and it’s about 3/4s full.
Old gaskets take a “seat”. They reform themselves until the pressure they used to seal the surfaces to them is no more. This may be part of the problem.
I say “may be part of” because your crankcase also vents through the Positive Crankcase Ventilation (PCV) valve. If that’s plugged it will allow pressure to build in the crankcase from the bypass gasses and force oil past old seals and gaskets.
And that bypass that builds the pressure can be greater on older more worn engines, building more pressure. As the compression rings and cylinder walls wear, and as the compression rings lose spring tension from all the heat and pounding, this can result.
First check your PCV valve. Actually, they’re cheap so you might even just change it. Then clean up the area and see if that stops the problem.
If it didn’t, you may want to run a compression test. If the engine is worn out, you may have to accept this. If not, and you feel up to it, you could try torquing the bolts around the oil pan or even changing the gasket. Be sure to use the right torque and pattern.
And check your oil filter to be sure it’s not just leaking at that seal and migrating.
Check your oil sending unit also. My mechanic spotted a leak from the unit on my Caprice at its last oil change. The leak wasn’t hitting the exhaust so I didn’t smell anything.