rt138See the RT-138 Maintenance Manual, Section 4.2. 3.3 RT-138 Overall Performance Tests See the RT-138 Maintenance Manual for wide band tests. All narrow band tests are performed withDATA & SPECIFICATIONS RT-138 Issue 1, Page 11 13 Cylinder oils of excessively hh BN for the fuel sulphur can lead to excessive piston crown deposit accumulation. Piston crown deposits need to be carefully monitored