Lakeside is absolutely right about the synthetic oil vs. the dino oils. With todays cross hatching capabilities you are actually better off to use a syn over a dino. In order to understand this I will try to explain what happens on a microscopic level when an engine breaks in with the different oils...
Engine broke in with dino type oil - on a microscopic level, metal pieces or the rough edges that must seal or mate to one another, break or chip off = longer break in time and more wear, it breaks off because the oil can't provide the shear or friction protection capabilities to keep the metal edges from hanging and chipping. The metal edges chip and wear down until they have a good smooth sealing surface.
Engine broke in with syn oil - on a microscopic level, the metal pieces or surfaces are rounded and smoothen down instead of broken off = almost no wear and quicker seating or sealing.
These two different break-in methods or rather oils used for breaking in an engine have been proven on larger engines on engine dyno's. The dyno's, when synthetic oil was used as a break-in oil would show the engines to be pretty much seated up and broke in after 3 - 5 pulls, where as a normal dino oil would take nearly all day to get the same "nice patterned or charted" dyno readings.
However I have heard, from some of the older engine builders, that the longer an engine takes to break in, the longer it would last. This really makes no sense to me, since it would appear that you would have more wearable material if the engine broke in quicker. I know people who have broke in engines with syn haven't had many to if any problems doing it as long as the machining is good and consistant... (if the cylinder has "all around" type cross hatching and machining, it has shown that you are better off to use a dino oil and let it break off the edges since the cylinder has to be reshaped anyway / good machining = no problem)
