There seem to be many schools of thought on this issue.  For many modern cars, I hear you should just drive normally, and don't change the oil early (because they use a special break-in oil).  I've always just done what my manual says.  I most recently broke in a new motorcycle so the following article is of particular interest to me.  Note that he says this applies to all four stroke engines:

www.mototuneusa.com/break_in_secrets.htm

What do you think?

Just drive it like you stole it!  When I picked up my Lightning off the dealer lot, I left 2 stripes out of their driveway about 60' long...

I try to do a variety of driving speeds for long periods, rather than a bunch of Cold starts and 3 mile trips.

I've heard that taking a new engine on a road trip is bad because your whole break in is at one RPM range.

break in oil is thin as hell, so whatever you do don't leave it in too long........................3000 miles at the latest, i'd change it from 1500-2000

On my bike, I didn't really go on rides that were less than 10 miles for the first 600 miles.  I also tried to vary the engine speed a lot, and push it every once in a while.  By push it, I mean I would take it to 9,500 RPM for a very short burst (my redline is at 14,000).  I changed the oil at 600 miles.

Quoted: www.mototuneusa.com/break_in_secrets.htm

That's an interesting article. He's not the only guy who recommends "working it hard" during the break-in period - David Vizard also comes to mind.

Might break the engine in faster, but I'm not convinced that it doesn't come at some penalty in ultimate engine life. Getting 200K out of a set of rings isn't exactly a top priority for a racing engine, but it is for your average daily driver - which might help explain why every single manufacturer recommends the "nice and easy" approach. If the"work it hard" approach was valid, you'd think that someone in the OEM community would be recommending it.

Drive it like you normally would.  Change the break-in oil at about 1500.  Run regular oil for about 10k in order to seat the rings.  Then switch to Mobil-1.

I don't know about longevity, but I don't know of any motorcycle race teams that break in a new or freshened up engine before it is practiced and raced with.

Dave

I'd follow what the manual says. Break in oil has special additives to help your engine break in, so if you change it earlier than suggested your car might not break in properly. If you follow what the manual says you shouldn't have a problem. Most people that have problems down the road most likely didn't follow the break in procedure that the manufacturer suggested.

Usually, the break in method is something along the lines of don't take long trips on the highway because you don't want your car breaking in at one RPM. Vary RPM's while driving through the whole range. It's not that complicated. Usually just normal daily driving is fine. You just don't want to buy a car and take it for a long trip right off the lot.

I know there are a lot of different suggested break in methods out there, but the people who engineered the car are going to know best how to do it. Engines and technology constantly change, so a third party break in suggestion might actually be slightly outdated and not the best way for you engine.

Break in oil has secret magical juices.

Interesting theory, but:

Lets say that piston is 6cm across and the clearance is .04mm.  Thus

The vacant area that the ring fills consists of only 7.59 sq/mm.  This tiny area is stretched into a gap about 18.975 cm long.  What's my point?  I'm not a mechanic or engineer, but I suspect that the gas pressure allowed through this gap is rather insignificant to the rings outward pressure.  He ingnores the fact that whatever gas was able to get 'behind' the ring, will have to overcome the friction between the ring and the ring gap cut into the piston.

He may be right about 'squaring off the rings', but that's probably achieved by abrasive wear due to increased piston speed, not due to gas pressure behind the rings.

I could be wrong...

Either way, I'd be more concerned about the lack of honing of the bearing surfaces and the lack of work hardening of the gears in the transmission (and differential if a car) than I would for the initial compression in a engine that needs to go a long time...


FIXED THE OBVIOUS MATH ERROR...

GM goodwrench has a article alot of people follow to break in their new engines.
It consists of half throttle spirts to 50 then letting the compression work the other way by letting the gas go until 20 mph.

Some say you need to rev the engine at around 2000-3000 for 10-20 minutes to break in the cam.

I found most newer engines are roller valvetrains so no more break in of the valvetrain is required.

The rings are the only thing left to break in and some claim with the modern machine work, they really don't need to be broke in at all anymore.

One thing that everyone agree's on(except in that link I just read): Take it easy on the engine for the first couple  thousand.

Want to do it the technical way?

Drive it in a broad variety of driving conditions until the first oil change.  At that oil change, have a magnetic oil plug installed.

Now go on a schedule of oil changes at EXACTLY 3000 miles, as precisely as you can POSSIBLY manage.   Each time,  have all the metal shavings harvested off the magnet,  clean them, dry them, and weigh them.

When the shavings/metal dust all but completely stop accumulating on the magnetic plug,  your engine is broken in.  At this time,  put in a Slick 50 or other competing superlubricant with your oil treatment, and run regular oil one more time.    At the next oil change, switch to synthetic oil like Mobil 1 or, if you're really feeling cocky, AeroShell.

Retreat with Slick 50 or whatever you used about once every 50,000 miles.

The engine should now outlast every other part of the car.

CJ

Quoted: Want to do it the technical way? Drive it in a broad variety of driving conditions until the first oil change.  At that oil change, have a magnetic oil plug installed. Now go on a schedule of oil changes at EXACTLY 3000 miles, as precisely as you can POSSIBLY manage.   Each time,  have all the metal shavings harvested off the magnet,  clean them, dry them, and weigh them. When the shavings/metal dust all but completely stop accumulating on the magnetic plug,  your engine is broken in.  At this time,  put in a Slick 50 or other competing superlubricant with your oil treatment, and run regular oil one more time.    At the next oil change, switch to synthetic oil like Mobil 1 or, if you're really feeling cocky, AeroShell. Retreat with Slick 50 or whatever you used about once every 50,000 miles. The engine should now outlast every other part of the car. CJ

Not Slick 50!!!!!!!!!!!  I have a friend in Atlanta who has a car care shop.  He has remedied several situations where people have put Slick 50 in their cars.

I was there one evening when a customer brought in his relatively new car and it was banging the hell out of the hydraulic lash adjusters.  Customer was pissed, cussing his car as a POS, etc.  We talked to him for a while and then the truth came out.  He had put Slick 50 in his car the day before.  He was asked if it had been smoking or rattling beforehand.  He said no.  He was asked why he put that junk in and he said that a friend recommended it.  Sheesh.

Well, we fixed the problem.  Had to keep his car for 2 days.  Changed the oil, drove it around, changed the oil, etc.  It took about 3 oil changes to get it quiet again.  

The customer had a different tune when he picked up the car.  It was nice and smooth and quiet and the bill wasn't anywhere near what he had been fearing for a new engine.

My friend calls it "Slick 50 million" because the inventor probably made a slick 50 mil on this junk while reaming his customers.

I do agree on the Mobil 1.  That's all that has been in my 929 since it was broken in.

I have seen Mobil 1 recommended here, but how does Mobil 1 compare to Castrol Syntec or any of the other synthetics?  I have heard that they are about equal, but usually people talk about Mobil 1.  Is it because Mobil is really better?  Or is their marketing just better?

Sorry if this is a hijack.

Quoted: Not Slick 50!!!!!!!!!!!   My friend calls it "Slick 50 million" because the inventor probably made a slick 50 mil on this junk while reaming his customers.

I've been using Slick 50 for about 10 years now and haven't had a single problem.  My last car had 200,000 miles on the engine and was still running.  Before I started using Slick 50 I locked up two engines.  Since then I have not lost an engine or had major engine problems while using Slick 50.

Does it help?  I don't know but I sure haven't had any problems with it.