my dad was an old school mechanic that worked on rolls royce p 51 d engines in world war 2 and diesal and all types of gas engines as a mechanic for 35 yrs at a dodge dealership and he told me once how to break a engine in a car was to run it at different throttle settings ie50mph then 30 mph for 5 or ten mins each time til it had about 100 moles on it then drive it normaly for next 500 miles not drag racing style but then he went on to say if u had a lead foot just floor it its gonna break any way u drive it so it wont matter anyway ur engines will always be in the shop a very wise no nonsence man i think