Getting ready to send off my first sample to Blackstone for a UOA on my 2005 Tacoma. Original OCIs were 3k but wanted to try 5k to see how the Castrol GTX 5w30 looks. The info from Blackstone suggest getting a TBN if your interested in extended OCI. Not sure if that means beyond my sample mileage or not. Should I get the TBN?