Hey everyone,

I am fairly new here and have a question about W140 diesels. I own an '84 300D with the OM617 and was wondering how the engines they put in the W140s compare. I know they came with the OM603 and OM606 I6 engines that also came in the W124s. I know people consider the 124s super reliable but I'm not sure if that just goes for the 2.5L I5 engines they came with or if those 6cyl engines were bulletproof as well. My dad really likes my car and is looking to get something similar but he's considering the idea of something more modern feeling like the W126(not much different than my 123), W124, or W140.

Are those decent engines? Or should he be looking for a 2.5L 124 instead? I have looked around a good bit and can't find a ton of information on them except a couple 10+ year old posts on here where people mention head gasket issues in the 6cyl. Something about the fact that Mercedes switched to an aluminum block?

I'm a noob so thanks for the help,
-Bret