Ive seen some literature online, and I am just curious. For those of you who know about it, what are the main differences between FA-4 and CK-4 spec HDEOs? I know that CK-4 is backwards compatible with many of the previous CX specs, but FA-4 isnt. There are claims that FA-4 is supposed to protect as well as CK-4 HDEO oils at lower viscosities. Does this have something to do with the lower HTHS viscosity as to why it isn't backward compatible?
I know up until recently, many HDEOs were dual-rated CK-4/SN, and then many still are. Valvoline Premium Blue and the Fram labeled HDEO is as well. How would the FA-4 spec fit into this? Would it be a bad idea to run it in a gas engine, or at least, any worse than running a non-dual rated CK-4?
I know up until recently, many HDEOs were dual-rated CK-4/SN, and then many still are. Valvoline Premium Blue and the Fram labeled HDEO is as well. How would the FA-4 spec fit into this? Would it be a bad idea to run it in a gas engine, or at least, any worse than running a non-dual rated CK-4?