Apple says max memory 8 GB for my MBP but It actually supports 16 GB

RAM prices have dropped incrediably low for these 2012 machines.

There is a slight performance hit, having unmatched pairs.

I would go with the full 16GB

Apple Mac Memory/ RAM Upgrades from OWC

MacBook Pro (15-inch Mid 2012), macOS (10.13.6), i7 480GB SSD 16GB RAM

Apple publishes a maximum RAM capacity when the computer is released which are based on then current RAM technology. However during the life of that computer model RAM manufacturers often release RAM upgrades which increases the capacity. To my recollection Apple has never revised a computer spec sheet to reflect the new capacity.

Hello,

Apple’s published maximum values are strangely conservative. People upgrade those machines to 16 GB all the time.

However, I doubt 10 GB would be worth the effort, assuming you could even find a 2 GB DIMM chip for that machine. Just upgrade it to 16 GB.

But then again, 8 GB should be plenty. If your machine is running noticeably slow, then perhaps you have some runaway software or adware. If not, your hard drive could be failing. An SSD will give you a performance boost greater than any memory upgrade.