Wow, a lot of tension over this, I would not argue right or wrong here. I will tell of my experiences, I always used Valvoline 20 50 in a 302 Ford I had, I broke it in with it and everything, one winter I went out and fired it up, it was about 25 degrees outside, I snapped the oil pump pickup, I was told that it snapped due to the oil, OK maybe. I was told to use a blend no higher than 40 by a speed shop. The latest engine in my stable was dyno tested, it was only run for about an hour maybe lessand then shipped in winter, most likely this is the worst thing to do to an engine, nothing has broken in and now don't run it for 2 months and let it oxidize, even the cam lube is gone by now. So the speed shop says to fire it up with Rotella, OK, its cheap lets see, feels nice, better than Valvoline. Granted this was 2 years ago. Things change. It occurs to me that we would want to use an oil that is the best all of the time not just for break in, if we drive them every day thats not so critical but most of us do not.
Now I'm not a cheap asz, so if it costs a bit more money thats OK because these engines are not cheap either. I have seen a couple of demonstrations of oils being run out on residue, one of those oils being Royal Purple, I have seen this oil run through a dyno and witnessed a horsepower increase. A number of years ago I witnessed the same things being done using Mobil One. I think that either of these oils would be the best type of oil to use for a break in due to these qualities. I understand that they are pricey, so what is the magic, the ZDDP, and you can buy a can of additive that has a lot of this ZDDP in it and presto you have a good break in oil? If the additive is the magic lets by all means put it in to our less pricey oil, but what should we use after that? The purple or the Mobil or the GTX? Personally I think I like the Purple, anyone see anything wrong with that?