I posted: "...This an opinion, not fact: I can't believe that ANY oil is going to prevent components from seating/mating together properly..." Follow up: I did not think about synthetic oils when I posted that. That's an intersting question on its own. (Synthetic lube oils are NOT recommended for two cycle Detroit Diesels last time I checked- these are the engines I operate.) What I was wondering was (1) Is John Deere trying to market a break in oil (that really isn't necessary), or (2) Is there something unique about John Deere Engines that really requires a break in oil, and (3) What do other engine manufacturers recommend, if anything, regarding special break in oil. For example, I thoroughly researched Detroit Diesel two cycle engine lubrication requirements two or three years ago and did not see anything about using break in oils. They basically said use MIL SPEC 2104F (I think that's the number). But these are older designs and may differ from the latest four cycle designs and perhaps newer metal alloys. And of course I may have missed special requirements for rebuilt engines. In 1999, my mechanic ( DD certified told me after new rings, pistons and liners were put in my engine no break in (moderate speed) was required. In fact on the initial test run, we operated my boat at 2150 RPM (2300 is max) for about an hour while mechanics checked every nook and cranny. At Detroit Diesel.com I just checked all Service Information Bulletins and did not see any lube oil related bulletins. There was some interesting information on how to clean coolant contaminated lube oil from DD. Rob Brueckner Hatteras YF