Please advise. Adding 1/2 qt. oil for every 3 maybe tanks of gas. 1990 300e 2900cc. 137000 miles. MB dealer said his mechanic had no issues with car. Car passed DEQ easy. Lots of power . No smoke plume. No visible leaks. Some lifter noise at first startup in morning. Hard starting at first startup in morning or after sitting all day at work. How much oil use is to much, and what would make it start better?