Why yes, there is something better than new car smell, and it's that feeling of a brand new (or overhauled) piston engine.
You may never get to experience breaking in a new engine, no matter how long you've been flying. But if you do ever have the chance, it's important to do it properly. Whether it's fresh from the factory new, factory rebuilt, or recently overhauled, you want to hang on to this sweet feeling of newness for as long as possible. This means you have to treat your bird right from the very beginning of its engine life. You have to rough it up a bit.
While your new engine may shine like the star it is, the truth of the matter is that the inner wall surface isn't smooth. The reason you want to -break in- your engine is to rub off high spots on the cylinder wall and piston rings so those rings can create a tight gas seal for normal operation. Now, every from-the-factory engine is going to have specifications on how to break it in once it's installed. Field overhaul facilities will likely also provide similar information. This information may be more specific and should be followed to the letter.
Generally, following proper break-in procedure means using the proper oil. This is where break-in oils come into play.
Watch our video below or continue reading to learn about straight grade and multi-viscosity oils for engine break-in:
Using specific oils with limited additives for the break-in period increases friction. Now, normally we use lubricants to reduce friction and metal-to-metal contact. However, this wear and tear during the initial break-in process prepares the engine's internal components for takeoff and extended flight. What you're essentially doing is wearing your engine into a workable condition.
Aviation break-in oils are available as both straight-grade and multi-viscosity.
Straight grade aviation oils are free of certain additives and detergents that may prevent the oil film from breaking. During this process, you want the film to break down. However, because these lubricants are primarily used for break-in and cause wear, it's important that you quickly drain and replace them with a proper lubricant before you take flight. We also recommend draining the oil several times during this break-in process to remove any potentially harmful metal debris. The duration and lubrication for the break-in period vary, so you should refer to OEM or overhaul facility for specific recommendations.
The multi-weight oils prevent the undesirable -glazing- that can happen during the break-in process. Glazing affects lubrication and results in a poor gas seal and high oil consumption. These oils are designed to wear-in new or overhauled engines in less than 25 hours and can be used as an operational oil until TBO.
You should always follow either the engine manufacturer's or overhauler's recommendations when it comes to properly breaking in your engine.