Ok, I am hesitant to chime in here, but!!!
I think everyone should first know what "break in" oil is and why it is or is not used.
"Break in" oil has higher levels of zinc (ZDDP) in it, that is the only difference. So, why the extra zinc. The sole purpose for break in oil is to provide a layer of zinc on the camshaft lobes so the camshaft and lifters can break in. The interesting thing about breaking in a camshaft is, this is done when the engine is first started. It takes about 20 minutes of running the engine at the first start up for the camshaft to break in. Engines with flat tappet camshafts are generally assembled with assembly lube (ZDDP) applied to the camshaft lobes when it is assembled. This assembly lube provides the extra layer of zinc on lobes so the camshaft can break in. After the engines initial run, the camshaft is already broken in. At this point, the initial oil is drained and new oil is refilled in the engine. At this point, some manufacturers refill with break in oil, some do not.
Break in oil has absolutely nothing to do with any other part of the engine other than the camshaft and lifters. The theory of break in oil assisting in breaking in piston rings is not accurate.
So, some engine manufacturers fill the engine with break in oil until the first oil change, some do not. The break in oil provides this continued higher level of zinc in the engine until the first oil change. There are mixed opinions as to the value of break in oil since the camshaft is already broken in after about 20 minutes of running which happened on the engine dyno when it was first built.
So, does Yanmar use "break in" oil. JD says the engines are shipped with 15w-40 Plus 50 (I checked), but honestly, it really doesn't matter. At the first oil change, whether you do it at 50 hours, annually or 200 hours, the camshaft has long been broken in. So, at this oil change, you can put 15w-40 JD Plus 50 or any other API Class CH or higher oil. Refilling with break in oil at this point is doing nothing internally in the engine. Now, that said, if it makes you feel better to refill the engine with break in oil, it will not hurt anything because, again, the only difference is the ZDDP.
IMHO, it is so much more important to use a high quality oil (pick one) and change it regularly, based on the manufacturers recommendations.
Most engine problems do not occur because of the oil that was used. Engine failures happen mostly from: not changing the oil regularly, low oil level, starting the engine and increasing the RPM instantly before the oil has a chance to get through the engine, shutting the engine done without leaving it idle for a few seconds first and overheating. :good2: