Can I use DDR3 1600MHz RAM in a Mac instead of 1067MHz?

I'm trying to get a 16 GB (2x of 8 GB) RAM to boost my computer, even though Apple says that it's only 8 GB on macs, but we know Apple is wrong on that. However, when I searched the online shopping place, they only have 1600 variants.

Can I use DDR3 1600 RAM sticks in a 1067 Mac? …and what are the consequences? and when you buy a RAM, does the PC3-8500 things matter or not?

Hardware Specifications:
MacBook Pro 13″ mid-2010 running OS X 10.9.1 Mavericks
Running on 2.4GHz Intel Core 2 Duo
Currently have 4 GB installed (2x of 2 GB) that is DDR3 1067MHz PC3-8500

Solution 1:

You could add the 1600 MHz memory for your MacBook Pro even though it's designed for a slower memory (1066 MHz) - it ought to work, but you'd be better off buying from a place that accepts returns. Here's some relevant information from Crucial on memory speeds (emphasis mine):

Memory is designed to be backward-compatible, so generally speaking, you can safely add faster memory to a computer that was designed to run slower memory. However, your system will operate at the speed of the slowest memory module.

In "DDR3-1600 PC3-12800"

• "DDR3" is the type (and must be the same as what your computer has)
• "1600" is the data transfer rate per second specified in millions (the technical term is "clock frequency") - "1600" here means it supports up to 1600 million transfers per second - in your case, it will be slowed down to 1066 million transfers per second since that's what your Mac is designed for
• "PC3-12800" is the name used in the memory industry - 12800 indicates a peak transfer rate of 12800 MB/s (of course, the actual performance in your case would be brought down to 8533 MB/s, matching PC3-8500).

Solution 2:

Just tried this in a mid-2009 macbook pro. It almost works. If you replace only one slot, everything works fine, since "your system will operate at the speed of the slowest memory module", as @MK said. But if you replace both of them at the same time, it will NOT work, since the system will try to operate at 1600 MHz (the speed of the slowest memory module).

Update: Tried it again, but using a different memory, and it did not work at all. It seems that macs are indeed picky. (Both memories were 1600 MHz, 4GB - the one that worked partially was a Patriot, the one that did not work at all was a Samsung).