The OM601 (4cyl), OM602 (5cyl) and OM603 (6cyl) engines will be the most familiar to you if you're used to VW diesels (cast iron block/aluminum head w/lifter buckets). IMHO, the OM602 as found in the '87 190D 2.5turbo (very rare) and '90-'93 300D 2.5 will return the highest level of fuel economy, performance and reliability of any diesel engine North American MB offered to date. In addition, the chassis these engines are found in are far superior to the older model Benzes. For example, I own an older W123 chassis w/OM617 (cast iron block/head) that I rely upon for running errands, must-make-it-there trips, and backup, but my true love and object of my affection is a S124 chassis w/OM603 (6 cyl) for it's heavenly ride, handling, comfort, performance and fuel economy--there really is no direct comparison.