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I'm just wondering because people tell me different things regarding what to do/what not to do during break-in periods.

i was told by a mechanic that it's important to vary the rpm, so to drive the car at different speeds and rpms.

I was told by another person that I just need to drive it carefully and as slow as possible.

Does any of this matter?
 

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With modern engines the tolerances are so tight the break in isn't so significant. If you look in the owners manual it says not to do wide open throttle starts or brake hard for something like the first 600 miles. The mileage will go up some though as you get some miles on the car and do a couple of oil changes.

Not that I'm advocating it, but some things I've been reading lately suggest that a hard break in might be better. BMW 3 series cars are taken on a drive to something like 100mph, and subjected to hard brake testing. Corvettes are taken off the line and dyno tested to make sure they are making the requisite horse power.

Ok so I know the Insight is different, I wouldn't run it wide open in the lowest possible gear all the time, but I wouldn't concern myself too much about doing any sort of elaborate break in.
 

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The reason for varying the RPM is to prevent a ridge forming on the wall of the cylinders. As the engine goes up in RPM the piston rides a little higher due to the connecting rod stretching. This would only be a problem if you decided to take a hypermile trip across the country. Normal driving is adequate variation. Personally I would not floor it for the first 600 miles as Rick mentioned. Slamming the brakes on is never a good idea but particularly not when the pads are new. This is true any time the pads are replaced not just when the car is new. That story about BMW and Corvette sounds like urban legend or backyard macho mechanic talk, but what do I know about those cars. :roll: I do know that Aeroplane engines have a very specific break in procedure that includes varying speeds.
 

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b1shmu63 said:
As the engine goes up in RPM the piston rides a little higher due to the connecting rod stretching.
:shock: Sound like a bit of a stretch to me Kip :!: :p

In general its the "relatively" rough surface of the cylinder bores with a fresh hone on them (to _cause_ initial additional wear on the rings for a more precice ultimate fit) that is the main concern. The linear velocity of the pistons (RPM) has a major effect on how this initial wear progresses.

Vary the speed / RPM within reason for the first 600 miles or so and don't worry about it. :)
 

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There are two schools of thought on this subject. One says to baby the car and follow the owners manual to a tee. The other says to run the engine hard, like a race car driver.

I prefer to take the middle ground and after owning numerous vehicles over the years feel it's just not that critical, as I'm not keeping my cars for 50 years. Most people barely keep their cars for 3 years. Engine and oil technology is much better than it was decades ago.
 

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You have driven home to California now, correct? Then welcome to "all broken in land" Enjoy as you lern how to drive your baby. Smoothness and easy thermal cycles(?) *1 along with frequent oil changes will keep you going

*1 By that I mean, drive easy to normal until the car is fully warmed, and drive easy for a short while before you shut off. Going 70 and quickly pulling into a rest stop and shutting off is hard on the car. But so is idling, so not too much of that either.
 

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:badgrin: :badgrin: :oops: John, it's probably just a macho urban legend that I fell prey to, I'm just repeating what was explained to me in regard to large 8 cylinder engines. (In my work I use a micrometer so a little probably has a different meaning for me than most folk.) Still. :roll:
 

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I came to the same conclusion pondering this in the shop today. If someone knows why the speed should be varied, now would be a good time to speak up.

Nice tools John! No digital accuracy here. One of my micrometers is a 6" mechanical dial type I've had for decades. The other is an antique 1" calliper I inherited from my grandfather. He was a master mechanic working for Ford in the very early years of the automobile.

OK, in case Santa reads this forum, a 12 inch digital would be nice.
 

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Modern machining that can produce a micro-finish on mating surfaces has helped reduce the need for a stringent break-in procedure, though metallic break-in/lap-in particles are still created and left to circulate in the break-in oil and often don't get trapped by the oil filter. I always do my first oil change at 500 miles without fail on any new engine just to help get the particles out of the engine before they can cause premature wear. The freshly honed surface of the cylinder walls, as John mentioned, is there to help the new piston rings become seated to the cylinder walls and some very fine metal particles are created during this process that can make it past the oil filter. Varying the RPM and the load on the engine helps to vary the cylinder pressure within the engine cylinders to help seat the rings and also helps keep engine parts that experience high pressure loads, such as camshaft lobes and rocker arms, from experiencing premature wear from galling.

So where do the fine metal break-in particles go if they don't get trapped by the oil filter you ask? This may sound nuts, but the particles sink to the bottom of the oil pan where they can get stirred up back into the oil each time you run the engine. Try this: Drain the break-in oil into a drain pan and then let the pan of oil sit overnight. The next day, slowly pour the used oil into a recycling container until there is only about 1 inch or so of oil left in the pan. Hold the drain pan in the sunlight while slowly rocking the drain pan side to side and you will see the break-in particles sparkle in the sunlight. 8)
 
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