Run in procedure on new vehicle?

[Mactech]

Do I detect a tribologist view of engine internal workings?
Modern oils are certainly very different than oils of 25 years ago...and in many parameters, also better
I had never connected the oil film thickness with the centrifugal forces before and it is somewhat counter-intuative.
Thanks for the viewpoint!

 

[190]

Do I detect a tribologist view of engine internal workings?
Modern oils are certainly very different than oils of 25 years ago...and in many parameters, also better
I had never connected the oil film thickness with the centrifugal forces before and it is somewhat counter-intuative.
Thanks for the viewpoint!

Not a tribologist just an interested amateur. I spent a long time thinking oil pressure was everything but all it does is supply sufficient oil to allow hydrodynamic lubrication to work and to keep the bearings cool. oil pressure alone is grossly insufficient to support the loads involved.

It's not exactly centrifugal forces that make it work. Firstly and also counter intuitive; in spite of the fine tolerances a shaft is never concentric with the bearing. In simplistic terms this variable gap allows oil to be dragged around by the shaft rotation in a converging wedge which increases the pressure and supports the load. In the diagram consider the load is vertical from above as in a big end bearing. The high pressure oil film is at the bottom. The oil film thickness that supports the load is a function of the peripheral speed of the shaft (revs), the oil viscosity and the load applied.

One of the consequences of hydrodynamic lubrication is that the oil gets hot. We tend to think oil heats up as a by product of the combustion process but much of the heating takes place inside the bearings. This produces frictional losses proportional to the revs which is why in pursuit of economy targets, the manufacturers have produced low rev engines that use thin oil. Both of which are working against maintaining the oil film thickness.

 

[Mactech]

Yes, that's a very clear illustration
In motorsport, oil temperature is monitored on it's way to and from the engine, but the temperature of the oil 'at the coalface' is very obviously more than that.
Oil manufacturers tend to quote a maximum working temperature for oils, but I suspect it is something we cannot measure on track, especially if some of the oil has been used as coolant to spray the underside of pistons as on many turbo engines.

As an aside, I managed to get an almost completely unheard of main bearing failure on my 40 year old Formula Ford car last year using modern thin synthetic oils. They would have run on Duckams 20/50 back in the day!
Given the engine was freshly rebuilt at the start of the season, maybe we just allowed the thin oil (Mobil 1) to get too hot in the main bearings

 

[Gaz-M]

Right over my head... so what does that mean you suggest in basic run-in terms..?


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[Delayed Steve]

Right over my head... so what does that mean you suggest in basic run-in terms..?


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Yeah ! It tells you in your hand book, basic run in terms , keep below a certain speed and don't labour the engine for I think 1600 km.

 

[190]

Right over my head... so what does that mean you suggest in basic run-in terms..?


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In a long winded way it says avoid heavy load at low revs and don't be afraid of using moderately fast revs as that will actually aid good lubrication.

 

[st13phil]

They would have run on Duckams 20/50 back in the day!

Ahh, good old Quackams! That brings back memories

 

[theogeor]

I have few rules and I follow them all the time irrespective if the car is new or not
A. Very soft on the petals until working temperature is achieved. If you have oil temp then you monitor it as well if now allow 3-4 mins after max water temperature is achieved
B. Allow car to settle down and cool down a bit by slower driving before switch off engine .

For brand new car I follow the above plus I try not to exceed 3/4 of max revs but with softer foot on the petal. In the past I changed oil after the first 1k miles but have not done it recently
Worth noting as others did that some manufacturers test every single engine. Few years back on a visit to the Porsche factory that was shown to us as it was part of the production line and QA testing