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There seems to be three camps. The high extreme says "drive it like you stole it". The low extreme is "baby it". In the middle is "follow the manufacturer's instructions". Who is right?

I personally believe the manufacturer, who has produced millions of engines and has a vested interest in ensuring that those engines remain as trouble-free as possible, is the best source for general run-in guidance. Others disagree, and believe that the engine must be run hard for best results. And then there's the people who are terrified to rev the thing or use more than partial throttle.

So what is the truth? I suspect it lies somewhere in the middle, as usual.

In another thread I (unfairly) tarred the drive-it-like-you-stole-it crowd as "random internet yahoos". For that, I apologize; looking into this topic I discovered that unlike Global Warming, this is not settled science. There are elements of truth to the aggressive and manufacturer procedures, and both should be weighed by the owner. With this post I shall attempt to redeem myself somewhat.

Why does a new or rebuilt engine need to be run-in?
http://en.wikipedia.org/wiki/Break-in_(mechanical_run-in)
In general, any mechanical system needs a period of adjustment where the various moving parts "bed" and achieve the optimal fit with regard to each other. Doing this too quickly can result in the parts not bedding properly,leading to poor fit, excessive wear, and eventual failure modes.

For engines, the main thing is the bedding of the piston rings and cylinder walls. The goal is to condition the pistons and rings to have the best possible fit with good lubrication and cooling. Proper break-in will achieve this goal; improper break-in will not, and the engine will not perform as well and may fail prematurely. Linked articles go into more detail on this.

The "drive it like you stole it" camp believes that proper conditioning of the rings depends upon a fairly high level of cylinder pressure, which means that the engine must be run aggressively during break in. They believe that the manufacturer's break in regime does not provide that kind of high pressure. Arguments opposing that view claim that "normal" driving is sufficient to provide the required pressure, while reducing the stress on the engine.

Almost everyone agrees that babying the engine is counterproductive. Without fairly aggressive throttle use, the rings and cylinders never properly work in and the engine will suffer from low power, excessive oil consumption, and other ailments. So it seems safe to advise people NOT to baby new engines.

Another thing everyone agrees upon is that you should vary the RPMs. Do not set the cruise control and then drive across Texas. Constant running at a single RPM fails to produce the proper variety of pressure (and vacuum) to bed in the cylinders.

And, an engine is a complex device that operates under significant stress. It takes some time for all the moving parts to reach the best operating state-- Pumps, bearings, seals, electromechanical devices, catalysts, sensors, etc. I think it's fair to state that forcing the engine to run at 100% from mile 1 is going to be bad for the rest of the engine, regardless of the effect upon the seating of the rings and pistons.

But the argument rages, with almost religious zeal. Who is right? Who is wrong? Here are some opinions.

Drive it like you stole it
http://www.mototuneusa.com/break_in_secrets.htm
IMHO, it's difficult to believe a person whose website makes your eyes bleed. But he is passionate.

http://www.motorcycleextremist.com/Motorcycle-Engine-Break-in-the-Right-Way!.html
This is motorcycle oriented, but still applicable. The author is not extreme, but favors a fairly aggressive break in.


Follow the manufacturer's directions
The instructions provided by BMW (and most other car builders) seem to be to drive normally, meaning don't thrash the engine but don't baby it either.

http://www.popularmechanics.com/cars/how-to/saturday-mechanic-blog/how-to-break-in-a-new-car
Hey, the website name contains the word "mechanics", they must be right!

So who is right?
I must admit that after spending some time googling this I am finding myself less dogmatic about the manufacturer's procedure and leaning more in the "random-internet-yahoo" direction. I am becoming yahooified, if you will.

What does MINI say? From page 148 in the manual under "Breaking-in period", it ssys:

For gasoline engine, 4,500 rpm and
100 mph/160 km/h.

For diesel engine, 3,500 rpm and
93 mph/150 km/h.

Avoid full load or kickdown under all circumstances.

From 1,200 miles/2,000 km
The engine and vehicle speed can gradually be
increased.


What's interesting to me is what the manual doesn't say. It is very vague about how to drive other than to keep it below a certain RPM range and don't floor it, ever. Beyond that, I interpret the instructions to say "drive normally". Normally for me is like I stole it, however. So what to do?

For better or worse, here's my plan:
1) do what the manual says regarding RPM limits and throttle operation.
2) within those restrictions, drive conservatively but don't baby it. Accelerate and decelerate with enthusiasm, but don't be an idiot.
3) avoid strong acceleration until the engine is warmed up. Don't use more than 3/4 throttle.
4) stay off the freeway/motorway.
5) don't engage Cruise Control.
6) vary the load and RPM constantly. Run it through the full range all the way up to the limits stated in the manual.
7) past 1200 miles, gradually ramp it up to my normal driving mode.
8) don't bog it. Ever.
9) install the JCW tuning kit when it comes out :)

This differs from random-internet-yahooism in that I am not saying just drive the H E double hockey sticks out of it. I am saying drive it fairly aggressively, but respect the manufacturer's limits.

That's my Random Internet Guy opinion, then. Your mileage may vary.
 

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Nice one uke. I am therefore thinking I may have been too gentle in terms of revs ie, not exceeded 3k for the first 1000 miles, but all the rest I've done exactly ie no labouring no full whack and never constant speed. I am now ramping it up ! GREAT WRITE UP THANKYOU
 
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I'd like to add one further point that my salesman told me yesterday. He said the engines are broken in at the factory, and that's the reason you don't need to change the oil for the first 10,000 miles. So, given this is true, the engines are not exactly new when we receive them.

If one is of a certain age, the drive-it-like-you-stole-it when new method is counter to what we knew to be true much of our lives. I could tell a story of a 1967 Fiat that had an extensive break-in program and STILL blew a head gasket in its first months!
 

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Yes and I know of one lotus model that had running in oil installed at the factory. However a batch were released with a different oil.apparently no one knows what. These engines never ranproperly and many people rebuilt them so rumour has it.
 

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Almost everyone agrees that babying the engine is counterproductive. Without fairly aggressive throttle use, the rings and cylinders never properly work in and the engine will suffer from low power, excessive oil consumption, and other ailments. So it seems safe to advise people NOT to baby new engines.
...
I think what happens is when you baby it, ECU will learn your driving habits and because of that, your car will feel sluggish. Just need to reset the ECU. With that in mind, babying is okay as long as you give enough range of RPM. But this is just an opinion. lol.

If I were buying a used car with 30k or 60k or 90k miles, I'd take the babied car (especially if it was driven by a granny, with proper maintenance) any day over the normally driven one.
 

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I think what happens is when you baby it, ECU will learn your driving habits and because of that, your car will feel sluggish. Just need to reset the ECU. With that in mind, babying is okay as long as you give enough range of RPM. But this is just an opinion. lol.

If I were buying a used car with 30k or 60k or 90k miles, I'd take the babied car (especially if it was driven by a granny, with proper maintenance) any day over the normally driven one.
I think the ECU issue is separate from the break-in issue. I agree that the ECU will learn that the driver is an 80-year old great grandmother who only drives to church on Sunday and adjust performance accordingly. But for break-in, there seems to be a specific set of procedures that exist regardless of whether an ECU controls the tune or not. If there were no ECU at all, the break in procedure would be dictated by the drive-it-like-you-stole-it or the follow-the-mfg philosophy. Add an ECU and the procedure changes not a whit.

Why would you take a babied car over the normally driven one? From what I'm seeing out on the intertubes, a babied care is more likely to have issues due to glazing of the cylinder walls. It seems to me that the normal car is a safer bet.
 

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But there's a difference between normal and thrashed .I agree I actually bought a grannies car in a way. Toyota mr2 mk 2 at 6 years old had only done 24000 mils. I've no . Way of knowing how those were driven but it was garages at home and work, and very pampered. It lasted me another 12 years and when I sold it at 160000 it was still running like a dream using only 0.5 lr oil every 6000. I'm afraid I'd a car doesn't need running in then I'd argue it doesn't need thrashing either. Given the choice thrashed or nannieds I'd have t h e nannied car any day, BUT FOR ME THE MOST IMPORTANT THINK IS IT HAS BEEN LOOKED AFTER ie fluids topped up not thrashed from cold etc and regular oil changes. etc.sadly many people don't bother.
 

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At the end of the day, do what the manual says. Period.

When it says no break-in period is required, then that is when no break-in period is required.

At present a break-in period is advised for engine longevity and reliability, why that should be ignored baffles me.
 

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But there's a difference between normal and thrashed .I agree I actually bought a grannies car in a way. Toyota mr2 mk 2 at 6 years old had only done 24000 mils. I've no . Way of knowing how those were driven but it was garages at home and work, and very pampered. It lasted me another 12 years and when I sold it at 160000 it was still running like a dream using only 0.5 lr oil every 6000. I'm afraid I'd a car doesn't need running in then I'd argue it doesn't need thrashing either. Given the choice thrashed or nannieds I'd have t h e nannied car any day, BUT FOR ME THE MOST IMPORTANT THINK IS IT HAS BEEN LOOKED AFTER ie fluids topped up not thrashed from cold etc and regular oil changes. etc.sadly many people don't bother.
Thinking back to all the cars that I bought new (9 of them), I basically followed the break-in regimen I advocated in the previous post. I never had any engine issues with any of those cars, and they all ran sweetly with good power. My MR2 definitely got the full RPM range/spirited driving treatment during break-in, and it was fine. My latest new car, a 2003 Honda Civic Hybrid, has 168,000 miles on it and is still going strong.

The used cars (5) have all had issues, ranging from annoying to catastrophic. One has to wonder if a contributing or primary factor was improper break-in?
 
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