In my 11th month of owning a certified 2001 S430, with normal maintenance history, no accidents. My miles driven so far: 6,500. Vehicle mileage total 73106. No oil leakage showed on the garage floor at any time during my ownership. On 2 long road trips (5 hours and 3 hours, mostly 70 - 75 mph) I got the advisory message to add 1 liter of oil. The first time I was not near a Mercedes dealer, but I found an automotive supply store whose owner personally owned 7 Mercedes lifetime, and he made sure I put the right oil in the right place to exactly the right level (no more!) The second time I took it to my dealership, where the oil amount was corrected, the sensor was checked, and their mechanics found no visible evidence of leakage (such as splatter). [I was told by the service manager that a quart of oil every 600 miles was their demarcation line as to whether the the oil consumption warranted further work.] My question: Is this oil consumption--2 liters in 6,500 miles--well within the normal range, just barely within the normal range, or indicative of a problem? I am grateful to have your opinion, for this is all new to me. - Postcard Bill