No where on their website does it mention HDEO ad packs and since this is an HDEO section, I wouldn't try the engine cleaner until it was verified by the manufacturer...
Schaeffer Manufacturing is the OLDEST petroleum lubrication company in the United States founded in 1839 before #2, Standard Oil of Ohio.
Here ends your history lesson...
No where is the word "acceptable" used in the Schaeffer TDS... The correct verbaige is "meets, exceeds and is suitable for use for the following specifications"...
You may consider a mid-SAPS oil from Schaeffer Mfg. Their European formulation 8008 5w30 has a HTHS of 3.6...
https://www.schaefferoil.com/documents/288-8008-td.pdf