Wow there is definitely a lot being said in here and all over the board as far as opinions. There is a lot of mis-information being passed around.
First thing that needs to be clarified is the statement "When oil is colder its thicker". This is a false statement. Going back to the basics, oil is rated by viscosity which is the oil's resistance to flow or simply put an oil's speed of flow as measured through a device known as a viscometer. The higher viscosity of an oil, the slower it will flow ie thicker. Looking at the stock fill for the BRZ its a 0w-20 oil. This means a 0 viscosity at cold operating temperatures and 20 viscosity at operating temps of 210*. On cold starts you need oil to flow quicker ie low viscosity ie THINNER oil to help reduce dry run time. So that being said.. when oil is a 0w-20 its THINNER at colder temps
Next statement I saw was Breakin oil = Mineral oil and Synthetics Take Longer. First ill take the Synthetics take longer as a compliment! That means were doing something right cause that means we are reducing wear! Now I wont touch on that comment but you are seeing a lot more cars coming out of the factory with synthetics as stock fills. The statement breakin oil = mineral oil nearly knocked me off my chair. Break ins are a very important step of an engines life to maximize performance. Mineral oils are compressible and contain contaminants. Synthetics are engineered with the correct levels of detergents, anti-wear additive, zinc and phosphorus. Which would you want running in your car during this critical point of time... Dinos remains sucked from the ground or something engineered in a lab with years of R&D by scientists and chemical engineers? Personally, Id take the engineered synthetic.
Now I can try and explain what the break in process is in my own words but Amsoil did so nicely for me so heres a classic copy and paste for you right from the Amsoil site.
"The primary goal during engine break-in is to seat the rings against the cylinder wall. Properly seated rings increase compression, resulting in maximum horsepower; they reduce oil consumption and prevent hot combustion gases from entering the crankcase. To achieve this, however, the oil must allow the correct level of “controlled wear” to occur between the cylinder wall/ring interface while maintaining wear protection on other critical engine parts. Insufficient break-in leaves behind peaks on the cylinder wall that prevent the rings from seating. The deeper valleys, meanwhile, allow excess oil to collect and burn during combustion, increasing oil consumption. Too much wear results in cylinder glazing due to peaks “rolling over” into the valleys and preventing oil from collecting and adequately lubricating the cylinder wall."
So well said...
Better yet, here is the link to the Break In oil that Amsoil offers. Take a read to the knowledge on this page.
http://www.amsoil.com/storefront/brk.aspx?zo=5001506
There is more to just piston seals that is important and should definitely be considered.
Now that being said. Everyone is going to have their own opinions as to what they want to do to their car. My personal opinion... Follow the manufacturers guide. From my personal experience it has saved engines and gotten maximum performance. I personally have a 2006 Evo 9 that I now race on the track. I followed the manufacturers guide to break in and around 3K miles started upgrading the car. My car was always around 20-25hp higher then other cars with the same mods tuned by the same tuner. I now have over 65K miles on the engine with all the stock internals. about 45K of those miles are at high boost, high horsepower and high rpm track miles. The engine is still running strong, compression is exactly where it was day 1 out of the factory and the cylinder walls still look brand new.
Like i said in the Fuel Additives thread. To each his own on how you want to do with your car but hopefully I can provide some correct information to help guide you in making your own decisions.