I understand all new cars sold since 1996 have to be OBD11 compliant by law. I also understand that apparently my ’96 Bentley Brooklands is specifically not obd11 compliant, whatever that means. (Some users report that the Brooklands service manual makes multiple references to it being obd11 compliant)

How much of the Torque or OBD11 results can be trusted in my car please? Or does ‘not compliant’ just mean that all the error codes cant be detected and removed?

I particularly need to check some or all of the oxygen sensors and am wondering whether there is a way of interpreting the Torque or OBD11 results to tell me whether and which sensors need replacing.

My MPG suddenly dipped from 17 to about 12 and I replaced one sensor. But I am not sure the MPG actually improved much.

I suppose it is possible that (assuming all sensors are the same) the garage that replaced the sensor (based on some other garage running MasterCheck and it showing wrong values for one or both sensors) replaced the wrong sensor.