Oil

[stretch1940]

What is the best oil to break in a new 2.25 petrol engine?

[binch]

Look for a good mineral based 'Running in oil or Break in oil' with a high zinc content like:

https://penriteoil.com.au/products/10-tenths-running-in-oil-15w-40-mineral

And get an extra oil filter to throw away after the first run in period, when you bring it up to temp the first time.  Change the filter but keep the running in oil in for the first 500 or 600km.   The change the oil to a good classic engine oil for the duration, and change the filter one more time.

Oil is cheap compared to the engine  ;D

[Red90]

And load it up. You need cylinder pressure to get the rings to bed in before the bores glaze. The sooner the better.