From TDIClub

The most critical time for the engine are the first few hours of operation. All VW engines are first started at the factory, and are allowed to run continuously with special oil. This oil is then changed out, and replaced with special break-in oil. It is important to follow the first 1,000 miles advice, and moreso for the very first few miles when pulling out of the dealership.

Contents 1 First 1,000 miles 2 1,000-5,000 miles 3 5,000-10,000 miles 4 10,000-60,000 5 60,000-the life of the motor 6 Rules that apply for the life of the car

First 1,000 miles

Keep rpms below 3,800. Avoid steady rpms. Frequent firm application of power is strongly recomended up to 3,800 rpm. Avoid the use of cruise control so that you naturally fluctuate the power with your foot.

1,000-5,000 miles

Use the full 5,100 rpm power range. Avoid steady rpms. Avoid the use of cruise control. Frequent application of full throttle is recomended to help seat the rings. City driving is ideal for breaking in a TDI due to frequent stops and acceleration. Once you get to 5,000 miles change the oil and perform your first service per the manual

5,000-10,000 miles

Use of the cruise control is ok at this point since most of the initial break in has occured. Continue to use occasional full throttle accelerations to continue to seat the rings. You will notice the engine become slightly louder during this phase due to less friction from the engine breaking in (normal for a diesel to become louder under lighter loads). If your going on a long drive and you are using the cruise, every so often step on the pedal to accelerate up about 20 mph then coast back down to your preset speed.

10,000-60,000

This is when the rest of the break in occurs. The engine from the factory will check out with about 475psi of compression pressure out of the crate. It will take at least 60,000 miles to reach the peak pressure of 550psi. For the most part once you get to 10,000 miles your compression will be around 510psi meaning that most of the break in has occured.

60,000-the life of the motor

The engines I have seen so far using a 5w40 oil are maintaining 550 psi of compression pressure with over 200,000 miles on the odometer. The owners have followed the advice above and do not have any oil consumption issues. This also means that with the higher pressure the engine is more efficient returning optimal fuel economy and reduced smoke output.

Rules that apply for the life of the car

• When the engine is cold (below the first 3 white marks at the base of the temp gage) rev the engine to no more than 2,500 RPMs. The idea is that glow plugs are functional below 2500 RPMs, the combustion is more complete, and the engine warms up quicker. With a good synthetic oil, the engine will warm quickly,
• When the engine is warm (above the first three white marks) Rev the engine to no more than 3,000 RPMs. The reason for this is to keep the turbo on boost, clear the VNT guide vanes and apply firm pressure to the rings for optimal sealing against blow-by gasses. The rings need the boost to seal since its a turbo charged engine, babying the engine is detrimental and will lead to issues with compression if done so for very long.
• Don't let the engine idle for too long after startup. The only way to warm a diesel engine is to drive it under load.
• 
  An example of VNT variable-geometry guide vanes
  
  These tilt in accordance to power requested by the driver (aka, the go-pedal). Highlighting the importance of the second point, and introducing Intake Clogging. With higher RPMs of the engine, more boost is generated, keeping soot and gunk from accumilating, and preventing buildup which may hamper the range of motion of these guides.
• User manual suggests firm application of power. DO NOT "baby" the engine and drive like a grandma. After all, these cars were designed for the autobahn. As soon as the engine is warm, keeping it on boost, excersizing the entrie RPM range once in a while, and avoiding excessive idling and low RPMs will prevent carbon soot buildup, intake clogging, allow proper piston ring seating, allow for fuel mileage gains, and is considered generally good for the engine. That is to say, not to drive like a maniac, but drive it like it was designed for it. Maximum torque occurs at 1,800 RPMs, maximum horsepower at 4,200 RPMs, the happy medium is somewhere in the middle.
• Keep the engine happy. Keep in mind the auto-bahn. Enjoy the car, and do not worry too much about it. Common sense implied, but this engine is ment to be driven without much further thought.

Information written by TDIClub member Drivbiwire