I was thinking about this, so i did a bit of digging, from what i can work out running in oil is just really shite mineral, best suited to 'period' cars with bad tolerances and poor components/bearings etc. In my experience some assembly lubes are better than other at breaking up into your oil. Changing the oil after the first start won't hurt anything especially if your concerned over cleanliness when building., 50 miles with swarf will ruin any engine, any swarf at all wont do you good.

But again so many people differ on so many things,

Example puma racing recommend that you bed the rings in within the first 20miles and then go very easy for the next 500,

Other folks recommend driving the car very gently, regardless of rings and the load you put on the bottom end (bearings) is massive when you are running in.

Other guys say you should give it hell lol

do a google is funny how much they all contradict. Personally i would be dubious over using fully synthetic before its totally 'loose' and also about using running in oil for that long. There are some things they do agree on though, one of them is the first few miles are the most important.

But again different opinions etc.

Rob,