What is Break-In Oil?
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Engine break-in oil is a critical component of an engine rebuild. It allows controlled friction in low-load areas like piston rings. Additionally, it provides exceptional protection to areas with high loads, such as the camshaft and lifters.
An engine rebuild is a complex procedure that can take weeks or months to complete. The engine break-in process is the final step in the journey. This ensures that all surfaces within the engine are fully mated, particularly the piston rings and valvetrain. A proper break-in is vital to a successful build.
For this reason, it is crucial to choose the correct engine lubricant. Engine break-in oil is a specialized oil with a complex job.
They use conventional oils for two reasons: They provide both full hydrodynamic films and also allow for sufficient friction and heat to properly wear mating parts together.
Synthetic engine oils can actually prolong break-in time and potentially glaze cylinders, which will incapacitate proper ring seating. This is because synthetic engine oils inherently have lower friction coefficients.
How Do You Use It?
Depending on the application, break-in oil is used for 500 – 1,000 miles, or 10-12 full heat cycles, where you allow the engine to reach full operating temperature and cool down completely between cycles.
Use engine break-in oil only long enough to seat the engine. The abrasive wear caused by engine break-in can increase exponentially. Therefore, it’s important to change the oil as soon as proper break-in has occurred. This can vary greatly and is often determined by ring tension and valvetrain type.
If you’re unsure of break-in duration, contact your engine builder for recommendations. Since they design break-in engine oils for short-term use, the oil typically doesn’t have the level of detergents you’ll find in a fully formulated engine oil.
Break-in Oil vs. Regular Motor Oil
What is break-in oil? It’s typically conventional-based lubricants containing zinc/phosphorus (ZDDP) and moly anti-wear compounds. ZDDP forms a polar attraction to surfaces in the engine and creates a sacrificial layer. This prevents metal-to-metal contact in areas where a full-fluid oil film cannot exist. For instance, between cam lobes and lifters.
Molybdenum disulfide is a sulfate-based additive that protects against corrosion and oxidation while also reducing friction. We should note that it’s important that engine break-in oil contains an aggressive detergent/dispersant package to trap contaminants and metal particles, keeping them away from engine parts.