I have used Valvoline's MaxLife and I just tried Castrol's oil for high mileage cars. I originally tried Mobil1 but I got leaks. I am seeing an excellent cleansing property of the synthetics, but for the 300E it was too much: Leaks!
So I changed to the MaxLife and did so for several changes. Oil consumption continued to decline from 1 qt every 800 miles to 1 qt every 2,200 miles.
I have noticed the car seems to like the Castrol. Starts very well hot or cold, smooth running but it is too early to tell on consumption. I will update as soon as I need to add some.
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)