Break in period?

In ancient days one would drive a new car like a maniac, helping it to "break in" for about 5000k, then do a full tune-up.
I have a new 05 ZX4, and the manual recommends NOT stressing it for
~3000K, in order for the rings/pistons to work themseleves in. Is this really necessary?
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What's the Best Way to Break in a New Engine?
The Short Answer: Run it Hard! Why? The piston ring seal is really what the break in process is all about. Contrary to
popular belief, piston rings don't seal the combustion pressure by spring tension. Ring tension is necessary only to "scrape" the oil to prevent it from entering the combustion chamber. If you think about it, the ring exerts maybe 5-10 lbs. of spring tension against the cylinder wall.... How can that small amount of spring tension seal against thousands of pounds of combustion pressure on the way down? Of course it can't. How do rings seal against massive combustion pressure? From the actual gas pressure itself! The pressure takes the path of least resistance, which means it passes over the top of the ring, and gets behind it to force it outward against the cylinder wall. The problem is that new rings are far from perfect and they must be worn in quite a bit too completely seal around the bore. If the gas pressure is strong enough from a wide-open throttle, and then the entire ring will make contact with the cylinder surface, and it will wear perfectly into the right shape. The problem with "Easy Break In" ... The rough crosshatch pattern in the cylinder bore acts like a file to allow the rings to wear. The rings quickly "use up" the roughness, regardless of how hard the engine is run. There's a very small window of opportunity to get the rings to seal really well ... only about 20 miles! If the rings aren't forced against the walls, they'll use up the roughness before they fully seat. Once that happens there is no solution but to re hone the cylinders, install new rings and start over again. An additional factor that you may not have realized is that the person at the dealership who set up your vehicle probably blasted your brand new car pretty hard on the "test run". So, without realizing it, that adrenaline crazed set - up mechanic actually did you a huge favor! Here's How To Do It: Warm the engine up completely. The main thing is to load the engine by opening the throttle hard in 2nd, 3rd, and 4th gear. The best method is to alternate between short bursts of acceleration and deceleration. You don't have to go over 65 mph to break in your engine. Also, make sure that you're not being followed closely by another car when you decelerate! The biggest problem with breaking your engine in on the street (besides police) is too little throttle = not enough pressure on the rings or if you get stuck in slow city traffic. For the first 200 miles or so, get out into the country where you can vary the speed more and check the water temperature occasionally. The racetrack is the perfect environment to break in an engine! The combination of acceleration and deceleration is just the ticket for sealing the rings. I know the owner's manual says to break it in easy, notice that this technique isn't "beating" on the engine, but rather taking a purposeful, methodical approach to sealing the rings. The logic to this method is sound. However, some will have a hard time with this approach, since it seems to "go against the grain". The argument for an easy break - in is usually: "that's what the manual says" Or more specifically: "there may be tight parts in the engine and it might do damage or even seize if it's run hard." Consider this: If there is something wrong with the engine clearances from the factory you'll find out about it soon enough no matter how easy or hard you run the engine. As long as the engine is fully brought up to temperature before it's run hard, you'll never have a problem. If there are any parts that are tight enough to cause seizure, no amount of running will loosen them up and fix the problem! So why do all the owner's manuals say to take it easy for the first thousand miles? Good question ... Q: What is the most common cause of engine problems? A Failure to warm the engine up completely before running it hard! Q: What is the second most common cause of engine problems? An easy break in! Because, when the rings don't seal well, the blow-by gasses contaminate the oil with acids and other harmful exhaust by-products! Ironically, an "easy break in" is not at all what it seems. By trying to "protect" the engine, the exact opposite happens, as leaky rings continue to contaminate your engine oil for the rest of the life of your engine! Blow by is reason why it is necessary to change oil MORE often on a high mileage engine. The reason is that brand-new rings don't seat all the way around the 360 degrees of their circumference. The gas pressure from hard acceleration forces the rings to contact the cylinder around their entire circumference, which is the only way the rings can properly wear into the exact shape of the cylinder and seal the combustion pressure. Avoid idling the engine. There is no load on the engine, so the rings are just going up and down "along for the ride". Only a small portion of their surface is actually contacting the cylinder wall. The ring area that does contact the cylinder wears down the roughness of the honing pattern on the cylinder walls. Once the roughness of the cylinder is gone, the rings stop wearing into the cylinder. If this happens before the entire ring has worn into the cylinder and sealed, you will have a slow engine no matter how hard it gets ridden after that point. The difference between an idling an engine driving it easy, versus one being driven hard is that the rings don't get loaded for more than a split second and don't seal, and an engine is in 100% ring sealing mode.
mike hunt

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