Thanks to all so far and happy holidays, good info!

Sixto, Yes, I do like the sound of the OM603, it's satisfying.

31 years and no problems with #14 head. Original owner.

I have an 87 300D. If it is "losing a little coolant" then keep an eye on it and don't let it get low. Losing coolant is an indicator of cracks. I actually ran mine like that for 5 years or so. No oil in water/water in oil problems, just small cracks. I ran into trouble when transitioning jobs and relying on son who was driving the car to keep up with the coolant level. He didn't and it overheated/blew head gasket big time. upon inspection, there were cracks in 2 or 3 chambers. Pistons and cylinders all looked good.
Currently in the process of replacing head putting engine back together. When I was sourcing heads, I could only find an #14 head that was not cracked and installed that. last big thing I need to buy is an oil pump and then I will get the engine back into the car.

It’s a simple as don’t overheat it and maintain the cooling system. There’s literally nothing to it. It applies to any aluminum head. A lot of times things are really overblown on the internet and it’s 90% of the time user error. It’s just like people constantly breaking glow plugs on a 606. They just don’t know what they’re doing.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Simple but not always possible. You can take the best care of it you can but only from when it comes under your care. If you don’t know the car from new, you can’t know if it has overheated.

Lots of heads are made of aluminum but some tolerate overheating better than others.

Sixto
98 E320s sedan and wagon
02 C320 wagon