[Tannaton]

Originally Posted by AndyV7o

Indeed.
It can also have a bearing on oci's, plus is best not used in high output/high revving/both engines.
As previously mentioned, if you know what you are doing, drive gently, use short oci's etc it can be fine, the problem is most people dont know, use long oci's or miss them, dont use the engine appropriately, rev from cold and so-on...

Agreed - the widespread use of fully synth oils paved the way for oil change intervals to be extended from circa 6 to 12k miles to 18k +