I don't know a whole lot about how TBN is calculated using FTIR, but I did find out that most labs use the ASTM test for used oil, not new oil, because it requires a significantly different testing method. Most approximations of equating the used oil test results to the new oil test results is usually around 2.0 adjustment, which means the TBN would be around 7.4 (if this was the used oil test). 7.4 is in the range of most oils intended for use with low sulfur fuels.
If somebody is in the mood for a test, donate the oil to me, and I'll run 4L of this in my Outback for 7,500 miles, beat the snot out of it, and UOA it so we can see how it holds up