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What is the correct way to break in a new engine. I read somewhere the best way was hard driving. There was an article about this with dynos to prove that every engine that was driven hard during break in, came out with more power than the exact same engine that was broken in gently. The reason I believe was given was because the directions for break in have not been updated and the use of new oils nowadays allow for this. Is there anyone that can shed some light on this?
 

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Devil's Advocate. Just to cheese you off.
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2 Schools of thought.

1) hard break-in.

needs to happen in the first few hundred miles (double digits are best!)
warm up engine by idling to operating temp (5 minutes in 50* degree weather should be fine)
Whale on it. Excercise the entire RPM range, using HEAVY load (uphill or high gears, full throttle) as well as engine braking (deceleration using displacement and downshifting). making a few nice runs on the highway (preferably when there's not any traffic to confuse) up to 65/75 MPH followed by high-RPM downshifts (don't go past redline) to 45 or less, and back up again. It's best if you start this process as soon as possible in the engine's life, and drive it continuously for 100-200 miles before shutting it down. When you pull into your garage, you should immediately change the oil. Then change it again at 1000 miles.

Benefits: Supposedly the high pressure exerted on the piston rings followed by the backpressure of deceleration will help really seat the rings well, due to the fact that the crosshatch pattern on the cylinder bore wears down quickly. Believers in this break-in method claim that the rings need lots of pressure and lots of RPM's to seal properly, and that the "gentle" break-in will wear out the crosshatches before the rings have trued up to the cylinder bore.



2) Gentle method:

Keep RPM's under 4,000 for the first 1,000 miles. Excercise the RPM band, but do not LOAD the engine with lots of wide-open-throttle on hills. Don't downshift to slow down. Change oil at 1,000 miles or ASAP afterwards. Change oil again at the "regular" interval (3,000-5,000)

Benefits: People that believe in this method believe that the engine parts fit very tight, and that extreme tension placed on the parts will "break" the engine until the parts have seated with each other. This may have been the case a long time ago, but parts generally fit great from the factory nowadays. They also believe that high RPMs and high loads will wear the crosshatch pattern out faster and that there will be less time to get a good piston ring seal formed.


Take your pick. maybe do a search, there was a thread about "hard" breakins a while ago.
 

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I subscribe to the hard break in method myself. My car had a fairly hard break in, and runs fine.
 

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Driver > Car
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Used a gentle / intermediate. Gentle until 500 miles, then did a few hard runs until 600 miles, then changed the oil.
 

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I don't know what is better or not, and I had never heard of the "hard" break-in until I read it here on [FJ]. But the "hard" break-in sure sounds like more fun.
 

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I think you should break it in how you plan to run it for the life of it.

If you're just gonna casually drive it... then casually break it in. If you're gonna race, 1320 or road... then run it damn hard!
 

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I did hard break in and have had no problems. I have no idea what the hp levels are. but at least I haven't broke down or anything.
 
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