M103 Oil Consumtion
I have a '88 260e with about 130k miles on it that was using about a quart of oil every 1000 miles. I replaced the valve stem seals and conusmption is reduced to about a quart every 1500 miles - not too bad.
I did a little research and read that modern engines are more efficient at regulating fuel and temperature so the oil does not get diluted with water vapor and fuel like it did in older cars. The oil level would actually rise in some cars due to liquids getting into the oil. The other issue, especially with mercedes, is that the engines run at much higher rpm's. Some oil is left on the cylinder walls with each stroke of the piston so it makes sense more oil will be consumed with the faster running engines.
All this aside, I bought a ''92 300e that really used a lot of oil, about a quart every 500 miles. I put new valve stem seals on, same as my 260e, and it uses essentially no oil between 3000 mile changes now. New valve stem seals were the cure for this car.