Technical Running in 🏃

[Toshi 975]

An old mate once told me that piston rings bed in after the first few strokes of the engine and should be lubricated with mineral oil. Another very knowledgeable guy swore by the properties of fully synthetic oil for detergent effect and reducing engine wear but not suitable for running in pistons as that hint of wear is necessary for the rings to bed in. Also I read an article by a prominent authority on tuned 500 engines which said that synthetic 10/60 oil was most suitable and to use his words he said it is more robust at the higher temperatures these engines run at.
Based on that when I have built engines from scratch for first start up I remove the plugs, lubricate the pistons with light mineral oil then turn the engine over on the starter quite a few times. In the sump I use a budget synthetic oil for start up and detergent effect. I do this as it is never possible to absolutely clean all the channel in the engine. Then start the engine and let it run up to temperature and repeat this a number of times trying to run it for about 2 hours under no load with the occasional blip of the throttle. I have always been amazed how black the oil can get in that time when I drain it and switch to Mobil 1 10/60 synthetic.
Any thoughts on this

 

[fiat500]

An old mate once told me that piston rings bed in after the first few strokes of the engine and should be lubricated with mineral oil. Another very knowledgeable guy swore by the properties of fully synthetic oil for detergent effect and reducing engine wear but not suitable for running in pistons as that hint of wear is necessary for the rings to bed in. Also I read an article by a prominent authority on tuned 500 engines which said that synthetic 10/60 oil was most suitable and to use his words he said it is more robust at the higher temperatures these engines run at.
Based on that when I have built engines from scratch for first start up I remove the plugs, lubricate the pistons with light mineral oil then turn the engine over on the starter quite a few times. In the sump I use a budget synthetic oil for start up and detergent effect. I do this as it is never possible to absolutely clean all the channel in the engine. Then start the engine and let it run up to temperature and repeat this a number of times trying to run it for about 2 hours under no load with the occasional blip of the throttle. I have always been amazed how black the oil can get in that time when I drain it and switch to Mobil 1 10/60 synthetic.
Any thoughts on this

I feel very safe running on 10W60 because it covers temperature eventualities both below and above the expected range for engines. But I don't think any oil fully compensates for keeping the engine cool in the first place.
For running in, I use proper "running-in" oil when I can be bothered, and just dive in, driving the car normally without excessive revs or going beyond 50mph for the first 500 miles or so. At that point I change the oil for whatever is my current favourite.

 

[the hobbler]

I feel very safe running on 10W60 because it covers temperature eventualities both below and above the expected range for engines. But I don't think any oil fully compensates for keeping the engine cool in the first place.
For running in, I use proper "running-in" oil when I can be bothered, and just dive in, driving the car normally without excessive revs or going beyond 50mph for the first 500 miles or so. At that point I change the oil for whatever is my current favourite.

When I re-built the current engine in my Abarth replica, I used a 'high-zinc content' running-in oil for 400 miles and limited revs to about 3,000 (3,500 on over-run). I then changed the oil for another dose of the 'high-zinc-content' running-in oil and again did 400 miles, this time limiting the revs to 4,000 (4,500 on overun). At the end of the 800 miles I drained the running-in oil and filled the engine with Morris Oils 10/50 Nanno high performance oil, the oil that I normally run my engines on. I concede that there is peobably no 'proper' way to run-in an engine, a case of "different ships, different cocoa". But as I always point out, oil is the life-blood of an engine, and even expensive oil is a darn site cheaper than a 'goosed' engine! I may be old-fashioned (Ann's version is somewhat stronger!) but I still believe in running an engine "in" carefully.

 

[Goldnrust]

Running in is a right can of worms… and a subject where you will have proponents of several different schools of thought, who are all convinced their way is the best way (myself included!!)…

What I think can help clear the muddied water a bit is to understand that there are several different systems in an engine and each are looking for different things from ‘running in’.

For example, a brand new cam shaft has to break in and settle with its lifters. That cam love to lifter meeting point is put under a lot of pressure, so you want a high zinc oil to help reduce friction, and you want to have lots of oil pressure / flow but under minimal pressure from the valves pushing back against the cam. So most cam manufacturers recommend holding the car at a high idle (2-2.5k rpm) for 20-30 mins for best cam shaft break in.

A new set of rings, on the other hand, need to pushed hard into the cylinder walls when the fresh jobs is at its sharpest in order to achieve the best sealing. For this you don’t want too much oil, or the bore could glaze, nor for the oil to be too slippery, or the rings might not bight into the sharp hind well enough to wear to that perfect seal. Running in oil is specifically not as slippery as a high end synthetic oil for just this reason.

This means as soon as there’s a bit of temp in the engine that some short bursts of 3/4 or even full throttle, up through the rev range is what’s needed. Each burst of throttle pushes the rings hard into the cylinder walls and helps them conform exactly to the bore. This is followed by a longer time coasting down, allowing time for metal particles from the rings and hone to wash away and for the rings to cool.

That same ring / fresh hone interface creates friction, which is why a new engine feels ‘tight’. which in turn makes heat. So you need to not run the engine too hard till it’s loosened off, or you risk over heating, and again possibly glazing the bore.

So that’s just rings and cam, and we’ve already got contradictory needs for the ‘ perfect’ run in, there’s a lot more to an engine that just rings and cam.

In my opinion, a camshaft break in done right is a priority, after that, or if you don’t have a new cam, then similar to @fiat500 I just minimise idling, lugging the engine and prolonged high speed runs for the first couple of hundred miles but otherwise just drive.

 

[fiat500]

When I re-built the current engine in my Abarth replica, I used a 'high-zinc content' running-in oil for 400 miles and limited revs to about 3,000 (3,500 on over-run). I then changed the oil for another dose of the 'high-zinc-content' running-in oil and again did 400 miles, this time limiting the revs to 4,000 (4,500 on overun). At the end of the 800 miles I drained the running-in oil and filled the engine with Morris Oils 10/50 Nanno high performance oil, the oil that I normally run my engines on. I concede that there is peobably no 'proper' way to run-in an engine, a case of "different ships, different cocoa". But as I always point out, oil is the life-blood of an engine, and even expensive oil is a darn site cheaper than a 'goosed' engine! I may be old-fashioned (Ann's version is somewhat stronger!) but I still believe in running an engine "in" carefully.

I don't think anyone thinks that you shouldn't be careful when running-in an engine that has cost you much time money and care. But there is a prevailing argument that you can more easily cause negatives by being a bit too soft on it than you can by being too hard.
I've yet to take a rebuilt engine up to a mileage where significant wear has taken place, let alone premature wear, and at a wild guess I suspect that most others here are the same. But as I only deal with standard components and specifications, perhaps my experience isn't directly comparable?