Q: Using a 2x4GB PC3-12800 DDR3 1600 MHz type RAM on 15-inch, 2.53GHz, Mid 2009

It might or it might not. The problem is very fast RAM often requires latency to work with the computer. Without the latency pulses the RAM is unable to sync up with the computer's memory bus. I found modules for your model here: Apple MacBook Pro Memory - Intel Core 2 Duo 2.53GHz 15" MC118LL-A - DMS.

I have dealt with DataMem for well over 25 years. They are an exceptionally reliable vendor.

I don't know what your sources there would be. All I can tell you is you can give it a try. Either it works or it doesn't. Be sure the vendor has a reasonable return policy just in case.

My local supplier has it in stock, and on line:

http://www.canadacomputers.com/product_info.php?cPath=24_326_327_608&item_id=036 583

They have told me they ship anywhere. But why not ask....