This is from my friend who just got a Ford Edge and is on another forum.
The following in from a guy on there who is a Ford Mechanic.
Does this sound resonable for all engines or just Fords?
"Vary the speed for 1,000-1,500 miles (Don't set the speed control at 70
and drive 400+ miles when new) to generate a wide wear pattern on gears.
This will help eliminate gear whine. Don't change the oil for 3,000 miles
or so and don't go wide open throttle for 1,000 miles. You want rings to
seat and bearing surfaces to wear in easily. Don't put a full synthetic oil
in a new vehicle unless you live in a sub-zero envirinment. It is too slick
and can promote glazing cylinder walls.
The purpose of "Breaking In" an engine is to permit the wear parts to
"Seat" correctly. In the engines in our vehicles, the piston compression
rings will seat fairly quickly - say within 1,000 miles or so. The oil
rings may take a few more thousand miles to seat properly. Let's round
it off at 3,000 miles for full engine break in.
Oil ring scrapers are barrel-faced and initially have a very small
contact area on the cylinder wall. Within the break in period, we want
to prevent the formation of a "Pressure Ridge" and for the rings to seat
properly. It takes a fair amount of friction for the rings to seat
against the cylinder wall.
In a perfect world, we would like to have a small load on the engine,
operate it between 2,000 and 3,500 RPM and leave a margin of safety if
the cylinder hone, bottom end clearances, or overall engine control
deviates slightly from optimum specifications. (Another reason not to go
wide open throttle until you have completed your break in.)
I our "Next to perfect" world, the best action is to leave the "Factory
Fill" oil in the engine until the first scheduled oil change at 3,000 to
5,000 miles (or 6 months if you are not driving much). After that you
should put Motorcraft 5W20 oil in the engine. It is a partial synthetic
oil and is preferred by Ford engineering.
The problem with changing out the factory fill oil too quickly, is that
the synthetic oils (including Motorcraft 5W20) are very slippery. If it
is introduced into the engine before the ring seating is complete, it
may cause the formation of a pressure ridge and glaze the cylinder
walls. This can lead to long term oil consumption problems and the only
way to correct is to disassemble the engine and re-hone the cylinders,
and start over.
It's not really a big problem or concern unless you start consuming more
than a quart of oil each 1,000 miles. But a proper "Break In" should
extend oil consumption to a quart or less each 3,000 to 5,000 miles. "