For your M103, stick with 15-40 Diesel oil Rotella-T. It is the best choice hands down. Keep change intervals every 5k and you'll have a long lasting, clean valvetrain. You'll also save a lot more money. $9/qt is ridiculous. Rotella-T is roughly $12/gallon which works out to be $3/qt

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
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2003 Gray Mercedes ML350 - 122k