Engine Drain Plug size

[JBK]

I have a 1995 GMC K2500 with the 5.7 engine. Would anyone know what size drain plug the base takes?

I had some work done at the dealer and the mechanic claimed I might need a new base pan because when he changed the oil he couldn't get the drain plug to seal right. He threw away my orignal plug (which I never had any trouble with!!) and put in a new plug. The part number he used is 11562588 which I believe is a 12mm plug, I have read where a 95 takes a 1/2" x 20 and wonder if he used the wrong size plug. If so I hope the threads in the base aren't damaged.

It's not leaking now but don't want to take any chances!! Again I never had any trouble with it and the truck only has 63,000 original miles on it. Any help would be appreciated, I'm wondering if I should go buy a 1/2" plug and change it out if the threads are ok.

Thanks in advance for any replies!

[SouthernSilveradoGuy85]

Not sure about the length and thread size, but the 5.7 in my old 98 took a 15mm socket. Drain plugs will get where they don't seal anymore because of the o-ring, but I would have liked to see how it wouldn't seal or at least shown the old one. I'm not sure if you could easily replace the o-ring or not though. I had my 98 for 10 years and did all my own oil changes, never had an issue with the drain plug.