My 1980 500SE (euro) has 172,000 mi. Other than replacing timing chain & rails about 20K ago, nothing has ever been done internally. I use about 1 qt. of oil every 800 to 1,000 miles. My left side head gasket has been leaking oil for the past two years. I am not experiencing any coolant loss and no oil is seeping into the coolant. I just did a compression check and the right bank is 195, 195, 195, 200 PSI and the left is 190, 192, 195, 195.

I am thinking of replacing the seals to see how my oil consumption improves. The problem is I still have the leaky head gasket. I hate to replace it if I do not need a valve job at the same time. How long can I live with a leaky gasket and do I chance having a catastrophic failure at some point?