All injection threads will be Metric, oil line fittings 'should' be parallel BSP, but the Indians have a propensity for using what comes to hand, so they might be Gas thread, Conduit thread of even Brass or Cycle thread.
All of these are detailed on our website in the "Mechanical Tables" section.
1/8" gas was the most popular taper and parallel thread for oil lines on English engines.
The 1/8" refers to the ID of the pipe and bears no relationship with the thread or the fitting, be warned!
Peter