The four ball wear test is certainly a valuable tool for use in developing lubricants, especially greases. My sharing of the Coke (and Chlorine bleach is even better!) was to point out that taking just one/that test as an absolute indicator of how well an engine oil will perform or using it as a gauge to compare with other oils, well, let's talk about Coke's performance....
I have a 4 ball machine in our lab and definately use it for our own comparative work, in fact it is well used but I will not be talking about any results with it for the aforementioned reasons..
We get a lot of "hmmm, that is very interesting" from the 4 ball and other tests, but the proof is in field performance. I have 6 inches of scar tissue from making lab assumptions and then having the lubricant proceed to totally fail in field operations..
George