When Is An Engine Broken In?

I've only got my own experience to go on, which is based on the totally different OCI culture in Europe.

Over many decades, I evolved my own running-in (break-in) schedule of never exceeding 50% of maximum rpm or 50% of maximum speed during the 1st 1,000 miles and then gradually increasing that limit up to 100% over the next 1,000 miles.

European OCI are notably longer than North America but dependent on a much higher minimum standard for engine oil - but like many petrolheads I change the oil at half distance but using the highest quality and widest multigrade available - the use of used engine oil analysis is almost unknown in Europe.

It's rumoured that factory-fill oil is a different specification to that recommended for oil changes but I've never seen any real evidence either way.

So my last GM car, a MY 2000 1.8i Family I Vauxhall Astra with a recommended 10,000 mile/1 year OCI using 10W-40 part-synthetic had an oil change every 5,000 miles using Mobil 1 0W-40 full synthetic (hydro-cracked, not German definition) for the whole of the 100,000 miles I owned it. During that time, it NEVER used any oil between OCI and ran sweeter than new all the way through.

I've had long debates on other international car forums about the long OCI and expensive European oil which meets the high ACEA standards - compared to more frequent changes with cheaper oil that's common in North America. Shortly after I bought my MY 2000 car, OCI generally were increased to 20,000 miles / 1 year.

As a family, the only engine we've run to destruction was a 1.2 Family I Vauxhall Nova which did the school run for 8 years and then became the adolescent son's chariot - disappointingly it only did 130,000 miles.

richmond2000 said:

Honda does/did say NOT TO CHANGE the engine oil for the first 12K Kms because of a special factory fill oil + I have heard 20K Kms before switching to full SYN unless your car came with it IE DEXOS oil is almost always syn/syn blend

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Here in the US, thru what 2005 / 2006 ? for sure ( don't know after that ) Honda used certain break in / initial fills...... which included among other things, a pretty good dose of Moly + a finer filtering filter.

If you knew how to go about it, you could 'duplicate' or obtain both the initial fill and initial filter.

More than one of each across the product line btw or at least for a while.

Saab had at least on the 2.3 an initial better filter for a long, long while as well.

As did some others.

Worth noting especially with regard to the wild, wild west - oops I mean the USA, factory fills and filters even if unexceptional in other ways tend to have a much stronger QC behind them, better handling along the distribution chain and net a greater consistency as well.


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Your OEM instructions ( Owners Manual ) as per Allstar are the best guide or place to start ..... well sorta' in ( at this point ) - in a 'mostly most often' sense.


Point being.... they are not all necessarily the same.

Furthermore, another variable is that not all user miles during break in are the same.


Excluding for a lack of information and knowledge the more exotic ring and bore material combos such as that new 'nanoslide' and similar stuff, the real custom answer includes when ( under a bunch of assumptions including following any and all instructions .... and in some cases, 'recommendations' ) - is when various wear particle groups flatten out - or reach normative values for that particular combo.


Some of the avoids and minimize rules and recommendations from the past are very likely at least still a good idea even if no longer required. In some cases, likely a real good idea.... or more irregardless of what some OEM info may say.


Also some of the post break in better things to do.

Then there is the post break in phenomena such as NHRAT101 mentioned to consider - ie well broken in prime movers and transmissions and third members etc with good followup use & care can in fact grow noticeably stronger and or nicer in more than a few ways thru 20 / 50 K US miles.


Way back when, had one or two that did the same for a lot longer than that.


Good fueling is or can be also part of this - one way or another.


Although this topic is complex and highly variable, and assuming no seriously derived and applied break in effort ( think along the lines of pads and tires etc ) treating the first 3 - 5 K and then the next segment up to 15 - 20 K differently than what comes next will never go out of fashion - or be a bad idea.

Even there though - depends, depends, depends.

Use of real synthetic Group IV and V and........ above ..... basestock lubes and oils can still be considered a separate consideration from the so called and mis named US market Group III 'Synthetic' product.


Part of all this relates to thermal cycling the equipment - X2 in a wide range 4 season climate exposure. Which is part of the reason I never consider a ring pack fully bedded in until much later than brand new -

Also..... the factory is recommending what's best from a factory point of view - which for damn sure is not necessarily the best from some other point of view.