Understanding Engine Color Codes

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Hundreds of Lycoming engines leave the factory monthly and are marked with a variety of colors on each cylinder. These colors have a definite meaning and provide valuable information about the engine. Questions concerning these colors and their meanings have been asked by many owners and maintenance personnel.

In the past, color coding of cylinders was confined to colored bands around the base of each cylinder. Today, new methods of painting (enameling) engines, and a need for quick, easy engine identification were instrumental in changing color code location.

The factory color code, a large painted stripe, is now located on the cylinder head between the push rods from the spark plug boss to bottom of the cylinder head. Additional color coding has been added to identify cylinders requiring long-reach spark plugs versus short-reach spark plugs. Location of spark plug identification color code is between the spark plug boss and rocker box.

Color Code for Cylinder Identification
  • Location – Between push rods on cylinder head, or band around base of cylinder barrel.
  • Engine gray or unpainted – Standard steel cylinder barrels.
  • Orange stripe – Chrome-plated cylinder barrels.
  • Blue stripe – Nitride-hardened cylinder barrels.
  • Green stripe* – Steel cylinder 0.010 oversize.
  • Yellow stripe* – Steel cylinder 0.020 oversize.

​*Color code applicable only to engines overhauled in the field. Lycoming does not sell oversize cylinders.

Color Code for Spark Plug Identification
  • Location – Fin area between spark plug and rocker box.
  • Engine gray or unpainted – Short-reach spark plugs.
  • Yellow – Long-reach spark plugs.
  • Caution – Use only approved spark plugs for all models of Lycoming engines. See latest revision of Lycoming Service Instruction No. 1042 for approved spark plugs.

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Related Publication

Service Instruction No. 1042

To learn more about the correct spark plugs for your Lycoming engine, please refer to Service Instruction No. 1042.