Brand new aircraft engines or engines that have otherwise been overhauled are recommended to be "broken-in" for a short time. The inner walls of aircraft engines are not entirely smooth when first machined, therefore it is recommended to run certain oils through the engine to allow the contacting metal surfaces to "seat" properly. The lubricating oils used for this process must have specific performance characteristics and differ from those commonly used once the break-in period is over.
This process actually requires some abrasion to the walls of the cylinder due to the rupturing of the oil film by the piston ring. This metal-to-metal contact is otherwise not desirable and will eventually lead to the collection of floating metal particles within the fluid - as such, it is recommended to drain your oil during this break-in process several times, so as not to cause excess, unwanted wear.
Straight Grade Mineral Oils are ideal for engine break-in due to their thinner composition and their absence of Detergent / Dispersants, which may prevent the breaking of the oil film. Of course, high power settings are also required for this phenomenon to occur. Should you require any advice on which oil is best for your new or overhauled engine, please call us at 1-855-899-7467.