MBreezy

Do you guys really think there is a break in period on our cars?? Ive read articles saying the best way to break in a new engine is by running it hard(something about piston rings, really not sure) and other articles, including our manual advises to be gentle with the car within first 1000 miles. Im still at 500 miles but ive pushed it few times already, I just feel that engines on bmws & benz's are built for performance and are put through plenty of strenuous tests which leads me to assume that the so called "break in" period is a myth. what do u guys think???

sameer13

I think it's a fact because you want to ensure that all parts are properly lubricated prior to running it hard.

clkwork

The first few hundred miles of a new engine's life have a major impact on how strongly that engine will perform, how much oil it will consume and how long it will last. The main purpose of break-in is to seat the compression rings to the cylinder walls. We are talking about the physical mating of the engine's piston rings to it's corresponding cylinder wall. That is, we want to physically wear the new piston rings into the cylinder wall until a compatible seal between the two is achieved.

Proper engine break in will produce an engine that achieves maximum power output with the least amount of oil consumption due to the fact that the piston rings have seated properly to the cylinder wall. When the piston rings are broken in or seated, they do not allow combustion gases to escape the combustion chamber past the piston rings into the crankcase section of the engine. This lack of "blow-by" keeps your engine running cleaner and cooler by preventing hot combustion gases and by-products from entering the crankcase section of the engine. Excessive "blow-by" will cause the crankcase section of the engine to become pressurized and contaminated with combustion gases, which in turn will force normal oil vapors out of the engine's breather, causing the engine to consume excessive amounts of oil.

In addition to sealing combustion gases in the combustion chamber, piston rings must also manage the amount of oil present on the cylinder walls for lubrication. If the rings do not seat properly, they cannot perform this function and will allow excessive amounts of oil to accumulate on the cylinder wall surfaces. This oil is burned each and every time the cylinder fires. The burning of this oil, coupled with "blow-by" induced engine breathing, are reasons that an engine that hasn't been broken in will consume more than its share of oil.

When a cylinder is new or overhauled the surface of it's walls are honed with abrasive stones to produce a rough surface that will help wear the piston rings in. This roughing up of the surface is known as "cross-hatching". A cylinder wall that has been properly "cross hatched" has a series of minute peaks and valleys cut into its surface. The face or portion of the piston ring that interfaces with the cross hatched cylinder wall is tapered to allow only a small portion of the ring to contact the honed cylinder wall. When the engine is operated, the tapered portion of the face of the piston ring rubs against the coarse surface of the cylinder wall causing wear on both objects.

Each tiny groove acts as the oil reservoir holding oil up to the top level of the groove where it then spreads over the peak surface. The piston ring must travel up and down over this grooved surface, and must "hydroplane" on the oil film retained by the grooves. Otherwise, the ring would make metal-to-metal contact with the cylinder wall and the cylinder would quickly wear out.

However the ring will only ride on this film of oil if there is sufficient surface area to support the ring on the oil. When the cylinders are freshly honed the peaks are sharp with little surface area. Our goal when seating the rings on new steel cylinders is to flatten out these peaks to give more surface area to support the rings, while leaving the bottom of the groove intact to hold enough oil to keep the surface of the cylinder wet with oil. See illustration. At the point where the top of the peaks produced by the honing operation become smooth and the tapered portion of the piston ring wears flat break in has occurred.

When the engine is operating, a force known as Break Mean Effective Pressure or B.M.E.P is generated within the combustion chamber. B.M.E.P. is the resultant force produced from the controlled burning of the fuel air mixture that the engine runs on. The higher the power setting the engine is running at, the higher the B.M.E.P. is and conversely as the power setting is lowered the B.M.E.P. becomes less.

B.M.E.P is an important part of the break in process. When the engine is running, B.M.E.P. is present in the cylinder behind the piston rings and it's force pushes the piston ring outward against the coarse honed cylinder wall. Piston rings are designed to take advantage of the pressure and us it to push the rings out against the cylinder wall. Therefore, as pressure builds during the compression stroke, the rings are pushed harder against the cylinder wall which aids in seating the rings.

The higher the B.M.E.P, the harder the piston ring is pushed against the wall. The surface temperature at the piston ring face and cylinder wall interface will be greater with high B.M.E.P. than with low B.M.E.P. This is because we are pushing the ring harder against the rough cylinder wall surface causing high amounts of friction and thus heat. The primary deterrent of break in is this heat. Allowing to much heat to build up at the ring to cylinder wall interface will cause the lubricating oil that is present to break down and glaze the cylinder wall surface. This glaze will prevent any further seating of the piston rings. If glazing is allowed to happen break in will never occur. Also, if too little pressure (throttle) is used during the break-in period glazing will also occur.

Most people seem to operate on the philosophy that they can best get their money's worth from any mechanical device by treating it with great care. This is probably true, but in many cases it is necessary to interpret what great care really means. This is particularly applicable when considering the break-in of a modern, reciprocating engine.

For those who still think that running the engine hard during break-in falls into the category of cruel and unusual punishment, there is one more argument for using high power loading for short periods (to avoid excessive heat) during the break-in. The use of low power settings does not expand the piston rings enough, and a film of oil is left on the cylinder walls. The high temperatures in the combustion chamber will oxidize this oil film so that it creates glazing of the cylinder walls. When this happens, the ring break-in process stops, and excessive oil consumption frequently occurs. The bad news is that extensive glazing can only be corrected by removing the cylinders and rehoning the walls. This is expensive, and it is an expense that can be avoided by proper break in procedures.

We must achieve a happy medium where we are pushing on the ring hard enough to wear it in but not hard enough to generate enough heat to cause glazing. Once again, if glazing should occur, the only remedy is to remove the effected cylinder, re-hone it and replace the piston rings and start the whole process over again.

We asked four top motorcycle engine builders what they do to ensure peak power output and optimum engine life. Here is a capsulation of their responses.
"If the wrong type of oil is used initially, or the break-in is too easy, rings and cylinders could (read will) glaze and never seal properly. A fresh cylinder wall needs some medium to high engine loading to get the piston rings to seat properly for good compression but make sure you don't lug or overheat the engine. Use high quality, low viscosity oil (Valvoline 30 weight), no synthetics, too slippery. If synthetics are used during initial break in the rings are sure to glaze over.

An engine's initial run should be used to bring oil and coolant (air, oil, and/or water) up to operating temperature only, with little or no load, then shut down and allowed to cool to ambient temperature. This is important. After each run the engine needs to completely cool down to ambient temperature. In Texas, especially in the summer, that's still pretty hot. After a cool down period, start it up again and take the motorcycle for it's fist ride (you hope).

This time give the engine light loads at relatively low rpm and stay out of top gear. Lugging the engine, i.e., low RPM with a lot of throttle (manifold pressure), is more detrimental than high rpm. Another key is too constantly vary engine load during the entire break-in period. A constant load is not ideal for breaking in bearing tolerances. This second run should last only 10-15 minutes before another complete cool down.

The third run should see slightly higher rpm with light to medium power loading using short bursts of acceleration to help seat the rings. Again 10-15 minutes of running should do it and again avoid top gear. A forth run should consist of light to medium engine loads with a few more bursts of medium-high rpm, and lasting just 10-15 minutes varying the engine load and again avoiding top gear. Next while the engine is still warm drain the oil and change the filter. This gets out the new metal particles that are being worn away. Most of the metal particles will break away within the first 50 -75 miles. To ensure the rings seat well, use the same high quality oil and don't be shy about short duration high rpm blasts through the lower gears after the oil has been changed.

A few more 15-20 minute sessions should be used to work up to the engine's redline gradually increasing the engine loads. After some definite hard running and 250-500 miles it's a good idea to check the valves. After 500 miles re-torqueing the head is suggested. Switch to synthetic oil but not before 500-1500 miles. Most of the engine experts warned of the danger of breaking in the engine too easily and ending up with an engine that will always run slow whether it is from tight tolerances, inadequate ring seal or carbon buildup. Engine load is more detrimental than rpm because of the head created internally, so avoid lugging the engine but rev it freely especially in the lower gears. Basically, be sure not to get it too hot but be sure to seat the rings properly.

clkwork

There's a lot on the Internet about this subject that goes both ways, that was just one example. Read up and pick a side!

For the most part I broke in my BS according to the book, at least that's my story if I ever need new rings

MBreezy

Good article....thanks for the info. i think its safe to say my first 500 miles have been a good balance of both methods, well at least i hope it has.

dmatre

I babied my Benz during the break-in.

However, my old Integra ('86) hit the rev limiter while still in the dealership lot. I ran it hard from day 1. A couple of years later, a couple of friends & I (who all autocrossed) swapped cars for some fun-runs. It was easily apparent that mine was the faster/freer of the three. This was noticed by them as well as by me. It seems that they babied theirs for the break-in, and I flogged mine.

I've got no data on longevity, however, as I had the engine torn down & rebuilt in '90 (at about 70k miles) to go ProSolo & Divisionals/Nationals.

That being said, I would imagine that if you're going to lease it, you can flog it - but I'm planning on keeping this one for a while, so I broke it in gently. As of now (108k miles), it still runs perfectly, hasn't burned a drop of oil, and seems to be as strong as when new.

Make of it as you wish, I merely present to you both sides of the story, from my experience.

PS: If you tour the BMW plant in Spartanburg, you will see the chassis dyno, where they run all cars coming off the production line at full throttle, to redline, in all gears. So much for coddling a fresh engine . . . .

TB5...

i drove for the frist 1000 the way i always drive...

meah.

FrankW

it's a myth and a fact.

in the old days fact

in the new, myth. engine components etc now-a-day are all built with much better precision. I think it's more important that you make sure you warm up the engine before you go instead of how hard you push it.

RLE

I think if you are going to plagiarize something, the least you could do is credit the source, even if it doesn't apply to any W204 engine.

Check the valves? For what? MB engines have had hydraulic lifters for nearly 25 years.

Re-torque the head? Maybe in the early 70s.

No synthetic before 1500 miles? MB's factory fill has been synthetic for almost nine years. Same for Porsche.

As to break-in, why not just follow the recommendation in the Owner's Manual?

FrankW

he did say it's from reading on the internet in his next post.

as for the recommendation in the Owner's Manual. if you really want to believe what MB lawyers are telling you.

Glyn M Ruck

Benz use MOS2 coated rings - with modern synthetic oils these things are hell to break in. Don't be too gentle on a new engine or it will never run in and it will use oil. It's crucial in the first 1000 miles to give the engine bursts at full throttle & make it do some work.

Caveats - Engine fully warmed up - watch engine temperature - you need only be careful if temperature rises above normal - You get the odd engine that is on the tight side of blueprint. If the engine is tight the temperature will rise. Never lug the engine at low RPM - let it spin.

Transmission components are made or broken in their 1st 150 miles of use. The only time care can be prudent while you wear off a few of the highspots on gears etc. After that it makes no difference.

CrAZyVeGAsBoY

+1 on this, but i still side on the err of caution but with todays tech its alot diff.

clkwork

1. I did say it was from the Internet. There's this thing called copy/paste that makes it a lot easier to read stuff on forums so everyone doesn't have to click the link.
2. Mercedes-Benz engines still have rings. That was the point.

norb

Yea, if it wasn't important, why would MB and every manufacturer for that matter, put in in the manual? On my car there is even a clear sticker on the windshield with the break in procedure. That's how important it is to MB.

Nevada Jack

I do not concern myself with "break-in" driving guidance. I picked up a S550 and GK550 and SL550 in Denver and drove them home in one day (800 miles) in about 12 hours. Never exceeded 90 or so and never used cruise control. Other than that it was drive the car...

Never had any problems of oil use, transmission jumps or any other problems. Had the S 18 months, the GL 12 months and the SL 8 months. I will treat the C the same way, i.e, drive it as I normally do. I won't have the 800 mile "break-in" trip but I will not baby it for 1000 miles.

I don't know how many videos I have seen on car building and they all show the finished car coming off the line and then to the test track.. flat out gunning it in all gear ranges and top speed tests. If it works at the factory then it works on the road out of the dealers showroom...

Glyn M Ruck

Only in America & you drive an E55

flagman

Anyone who has spent any time around automotive assembly plants like I have has seen the cars come off the the line and immediately go for some high speed runs down the test track to test noise, vibration, brakes, etc. So much for babying the car during the break-in period.

Also, if you think the car jockeys that drive cars around during shipping are gentle with them, you're in for a big surprise.

All this being said, I follow the break-in procedures to preserve warranty protection. Driving details are logged and can be downloaded off the system, so it's not difficult for the dealer service tech. to see if the problem you have complained about has been due to not following break-in procedures.

FrankW

i think they randomly pick cars for those tests, but every car that comes off the line goes on the dyno first and makes a full throttle pull to see if anything's wrong with it.

RLE

I tend to believe the manufacturer is a reliable source. BTW, warming up the engine beyond thirty seconds is unnecessary.

FrankW

like the reliable source that MB headquarter told many that TSB for the rear brake pads doesn't exist, right?

Glyn M Ruck

Let me clarify - I do not mean warming up an engine by idling. I mean by driving normally before demanding full RPM etc. If you don't do this you will accelerate wear & this is well documented by every OEM & oil company on the planet.

Glyn M Ruck

+1 this will give you everything that is desired. You want to avoid constant throttle for long periods of time.

AF330i

Bringing a 1 month old post back to the top ... I am interested in this ... are the driving details really logged in for this long of a time frame.

In other words let's say you have a problem 8 months down the road, can they really pull out a log and which shows in the first month of ownership you drove the car hard ?

Also who is to say it is not covered by the warranty if you did drove the car hard in the first month or two of ownership. What can the dealer tell you ... sorry sir you redlined the car at 110 miles as per this log and this is therefore considered abuse so you are not covered.

Not that I think you should go ***** out on a new car, I drive the car like I normally drive though a little bit on the 'easier' side.

Glyn M Ruck

The system is no where near that sophisticated. It can give you a couple of major parameters like the number of WOTs between one service and another. It can't date or time stamp them.

RabbitDad

Interestingly, my dealer told me to just drive the car normally from the go, no running in or nothing - just standard precautions like getting the engine warm and don't 'race' it for the first 1000 km or so. He said the engines are already run in at the factory. Not sure if that's true, but even I know that the manufacturing process nowadays eliminates a lot of the traditional need for running in.

However then I read the owner's manual and it advised a 1500 km break-in period . Anyway at that point I was already well beyond the 1000 km mark and just kept driving it as I would have any other car. Engine feels strong and healthy now (4500 km), so no complaints.

That's just the engine though. Other elements like brakes, tires and gearbox *do* need some running in (not more than a couple 100 km at most from what I understand).