What thread is my oil pan drain plug?

[dmanshane]

I have a 1995 c1500 5.7 and a 1997 c3500 with a 7.4 what thread is the oil pan drain plug? Parts stores have 2 options m12x 1.5 or 1/2”-20

 

[HotWheelsBurban]

I have a 1995 c1500 5.7 and a 1997 c3500 with a 7.4 what thread is the oil pan drain plug? Parts stores have 2 options m12x 1.5 or 1/2”-20

Pretty sure the 5.7 should be 1/2"-20. Both mine are. The hex head is 15mm though.

 

[Schurkey]

The trucks are 25+ years old. What they were born with may not be what they have now.

Remove your drain plug, measure the threads.