My car did its first 2000km with cruise control set at 90, and every on/off ramp taken at full bull. Also, the 10km test drive led to my salesman saying "Never seen somebody drive a stick shift so... well. How do you do that three pedal thing?"
Break in has gone the way of the dodo. Rings and gaskets are set these days with zero tolerance. Varying speeds and keeping it calm is to allow things to seat and settle. These days, that's a thousandth of an inch, not 3mm.
EVERY car ever sold has a dozen km of hardcore abuse on it. All I did was short shift for the first bit. Full beans, but kept it under 4500rpm.
I have no ticks or clacks, and am getting 7l/100 in -20C conditions, most days the car only starts blowing hot 20km into my 55km commute. My 3cyl Mirage is barely getting much better (6.1).
Closing in on 4000km, had it for a month and a bit.
View my fuel log 2018 Micra SV manual: 6.8 L/100 km ... 41.7 mpg (Imp) ... 14.8 km/L ... 34.7 mpg (US) ...