Thanks but I know the difference between valve stem seals and valve seals! Either way you look at it, having to do any of that work on an engine with just 140K miles isn't great engineering in my opinion. My friend has a Toyota Tundra with a 4.7L DOHC 32 Valve V8 engine that has 212K miles on it and doesn't consume a drop of oil and also has never had any such work done on it.

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1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver