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I appreciate the possibility that newer internal combustion engines (ICEs) burn more oil throughout their life. This appears to be partly due to using lower viscosity oils (which are being specified to achieve higher efficiency).

But I am also occasionally reading (on the wider web) that newer ICEs will burn off more oil during the break-in period. This is for example stated in this answer.

The oil consumption can be as much as 1 liter per 1,000 km during a running-in period of approx. 5,000 km if the engine is new or replaced (replacement of piston ring).

If it is indeed true that recent ICEs will burn more oil during the break-in period (5000? 10000? miles-kilometers?), why would that be so? What would consume oil during the first few thousands of the lifetime of an engine than the next stage of its lifetime?

My cast iron pans require an oil seasoning during the first several instances of use. This patina will subsequently protect the pan and will result in better performance (less adherence of food, for example). If I open a fully broken-in ICE and touch the cylinder walls, will I find a patina akin to cast iron pan seasoning?

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Oil consumption during break-in is a very real thing, but it has nothing to do with a patina buildup canceling it out. It has to do with how rings seat in the bores and thus better seal. Getting cylinder rings to seat has been happening since the ICE was invented, so increased oil consumption during break-in is not a "new engine" thing.

When an ICE is put together, the cylinders are given what is known as a crosshatch hone. The specifics of how this crosshatch is applied has to do the cylinder wall material, ring material, and engine use. When it is first applied, the surface, on a microscopic scale is quite rough. You'd see the crosshatching, but you might not be able to feel it. As the engine is run, the rings wear into the wall smoothing it out and blending the ring face into the cylinder wall creating a very good seal. In most gasoline (petrol) powered there are two top rings which seal the compression and provide minimal oil control. There are two lower rings which provide oil control and virtually no compression. Until these rings seat, it will cause a bit of oil consumption. Some engines are worse than others. Some ring materials seat very quickly while others do not. All of these factors add up to different amounts of oil consumption as well as different lengths of time for seating to occur.

Some newer cars do burn more oil, but it has been my experience this has less to do with how the rings seat and more so having to do with the PCV systems allowing oil to pass through them. GM LS engines get a very bad rap for oil consumption, yet when the right oil control measures are involved, it's almost completely eliminated. I'm sure other "newer" engines get the same bad rap for the same exact thing.

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    This is the answer. Further: Food grade oils on cast iron form a coating due to oxidation and polymerization. Motor oils are specifically formulated not to oxidize or polymerize, as that would form "varnish" then "sludge" in the engine. If you did ever manage to form a food grade oil patina on a cylinder wall, it would be scraped off by the rings within moments after starting.
    – MTA
    Commented May 7 at 16:00
  • @MTA Understood. My problem with going down your line of reasoning is that there is either an oil layer (of any form) between the cylinder wall and the cylinder, or there isn't. If there is an oil layer — during normal life after break-in — then that layer would be regularly burnt off, leading to oil loss, in any engine. If there isn't an oil layer, then we're saying that we have metal touching metal 1500+ times / minute (same as the rpm), and this scrubbing has to wear one or the other. What is happening, if neither?
    – Sam7919
    Commented May 7 at 17:31
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    @Sam7919 There is a very thin film of oil on the cylinder wall about 1-3 microns thick. (1000 microns in 1 mm.) See journals.sagepub.com/doi/10.1177/14680874221088547 There is no metal to metal contact between piston ring and cylinder. If contact ever occurs, the cylinder becomes scored. So in normal conditions the rings slide on a film of oil.
    – MTA
    Commented May 7 at 19:31
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    @Sam7919 The oil film does not burn off the cylinder wall because the film does not reach combustion temperature – not even close – even though it is exposed to flame. This is because the thin film of oil is in contact with the cylinder wall, which acts as a heat sink during the very brief time that flame is in the cylinder. The cylinder wall remains at a constant temperature a little higher than the coolant temperature, and this keeps the cylinder's oil film cool enough to survive the brief flame without itself burning up.
    – MTA
    Commented May 7 at 19:33
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    @Sam7919 - Here in the States we have warranties on vehicle's emissions equipment which far exceeds the length of bumper to bumper or powertrain warranties. Because of this, you won't see cats go bad as you're suggesting very often if at all. If it does go bad, you take it back to the dealership and get it replaced free of charge. And because of the federally mandated coverage, manufacturers are going to do what they can to mitigate any issues which might occur as you're suggesting, mainly because they don't want to have to pay for this on a bunch of vehicles.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented May 8 at 9:51

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