Multi-Grade 20w-50 oils are commonly used for engine break-in in most opposed piston engines.
With a Viscosity Index (VI) that greatly exceeds single-grade oil, these multi-weight options are primarily used at engine break-in, but some may be used in normal operation as well - to better determine which oils are permitted for a specific use, consult both OEM specifications and the respective product data sheets of these lubricants.
Some of the requirements met by these oils are as follows:
SAE Standard J1966, U.S. Military Specification MIL-L-6082 (obsolete), QPL approval number: N06L1-20W-50 (Type M), Avco Lycoming Material Specification No. 301G, Pratt & Whitney Service Bulletin No. 1183 Rev. U, SAE Standard J1899, Teledyne Continental Material Specification MHS-24B, and U.S. Military Specification MIL-L-22851D (obsolete) for additive treatment.
QPL Approval Numbers: D07L1-20W-50 (X/C 20W-50)
(Note: not every oil exceeds these requirements. Check product data sheets on the item pages for more information.)