The keys to proper engine break in, IMO, include not using cruise control, not nearing redline unless you motor is fully warmed up, varying your RPM's, and using compression braking to slow you down. If you want to know more, read on. If this seems overkill, no need to read more.
Regarding engine compression braking, one of the ways to best seat your piston rings is to raise your RPM's from 2,000 to 4,000 RPM's, then let the motor's compression alone slow you down. This results in the engine compression forcing the rings firmly against the cyclinder walls, creating the best possible wearing down of fractional high and low spots so that the piston rings seat fully and firmly against the walls.
By best seating/sealing your piston rings, lots of positive things happen including best compression -- which results in the most power, least oil blowby/oil usage, and as a result of the above, best fuel mileage no matter how you drive your car.
Specifically, I progressively raise the RPM range (again once my motor is warmed up), throughout the manufacturer's break in mileage recommendation. For example for the first few hundred miles I will in third gear for the first 300 miles, take the RPM's up to 4,000 RPM, letting engine compression slow me back down to 2,000 RPM's, but for the last half of the manufacturer recommended break in period, would take the RPM's up to 5,000 RPMs, then letting the engine compression brake me down to 3,000 RPM's. And toward the very end of break in period, would take my motor up to 500 RPM's below redline, then using engine compression braking, have it reduce my RPM's the same 2,000 RPM's.
Some will say "what a pain in the neck" the above regimen is. But doing this rev raising/engine compression braking process, which takes all of 30-40 seconds once every 15 minutes for the first 600 miles has never let me down, including never having an motor issue in 2,000,000+ miles, and only on one motor years ago, ever needing to add a quart of oil between manufacturer recommended oil changes.
