excessive smoking on 1990 Mercedes-Benz 420SEL

car smokes after being driven for half hour around town or up hill, car has 148,000 miles and has been resonably well maintained. It uses about 1 quart oil per 3,000 miles. Thanks.

Worn valve guides or failed valve guide seals and piston rings worn or sticky can cause that concern. Greg
Thanks-sorry to get bacxk so late