On our Ram 3500, the supplement diesel manual says the engine requires no break in. More to the point no towing extends the time for break in.
General consideration........Cummins
INITIAL BREAK-IN PERIOD = 1000 miles or less. During this period, the
piston rings may not have had a chance to
seat yet, which allows cylinder pressure to pass by the rings into the crankcase, causing blow by. After the initial break-in period, the
engine will need to be worked to create high enough cylinder temperature to seal the piston rings, which helps prevent blow by.
Vary the engine speed so the entire vehicle, as well as the
engine, becomes accustomed to varying speeds, loads,
rpm, etc. .
For on-highway, automotive applications, operate the engine at 1500 to 1800 rpm in high
gear for the first 50 to 100 miles. However, DO NOT idle the
engine for more than five (5) minutes at any one time during the first 100 miles.
For off-highway, non-automotive applications, operate the
engine at 75% throttle while loaded during the first three (3) hours. Again, DO NOT idle the engine for more than five (5) minutes at any one time. Also, DO NOT operate the engine at rated speed (
rpm) and full load for more than five (5) minutes at any one time.
MID BREAK-IN PERIOD. After the first 1000 miles, the engine is ready to be worked, which will help
seat the piston rings to avoid blowby and avoid carbon buildup to avoid fuel slobber because of
light load operation. If possible, drive in hilly or mountainous areas OR load the
truck with 700 - 800 lbs OR pull an empty trailer (tandem car-hauler type)*.
*NOTE: If you use a small single axle trailer, some load on the trailer is recommended.
Certainly everything with a new
truck will 'loosen up' after 40 or 50k miles, including the engine,
wheel bearings, brakes, etc. etc. We doubt that the engine torque or power will increase much, however. With light loading, the engine can take as high as 30,000 miles to be considered 'broken in'.
When the
bearings, brakes, engine, etc. do 'wear in', the
truck may seem to perform better, just because you will have less resistance from all these new components. The amount of fuel consumed by the engine may improve slightly after the break-in period, however, there are many other variables involved with the vehicle
chassis that will affect
MPG, more than the engine.
More from Cummins....
The mating parts in the engine should achieve final finish and fit during the first 6,000 miles with properly loaded operation. After the run-in period, you should achieve optimum power and fuel economy from your Turbo Diesel.
A lot of reading at
http://www.thedieselstop.com/content...iesel%20Engine