On the top of my Garrett 2860 there was an aluminum adapter for the oil inlet. I picked up another one to run -4 line, but the inlet is not 1/8 npt,, as it appears. It is something slightly larger, with a similar looking thread. Anyone know what it is?

 

1/4" NPT? 10mm straight thread?

 

Don't know if it'll help but the oil inlets on top of the chra of t25s and t28s I've worked with were 12mm threads