Optiplex 380 Mini Tower- Maximum RAM?

There are discrepancies on what people say the maximum RAM for the Optiplex 380 Mini Tower is.

I have a Optiplex 380 Mini Tower with a Core2Duo processor, running Windows 7 Pro.

There are two DDR3 RAM slots. I have a 2GB stick of PCE-8500 in one slot, and the other slot is empty. I'd like to bump it up the maximum RAM this computer will handle. However, I don't know what the maximum is.

* Dell's PDF service manual for the Optiplex 380 MT says the maximum is 4GB of PC3-8500

* Cnet's page on the Optiplex 380 MT says the maximum is 8GB of PC3-10600

* I see a computer on Ebay-( "Dell OptiPlex 380 Intel E7600 3.06GHz Core 2 Duo 8GB BRAND NEW 500GB HD Win7 Pro") that has 8GB ("BRAND NEW Crucial 8GB DDR3 ram installed  2 x 4GB, LOW DENSITY, RETAIL PACKAGE INCLUDED").   I even emailed the seller and asked if the computer uses all 8GB and he replied yes.

So I'd like to find our what the real deal on the maximum RAM is.

Is it possible that when the Dell service manual was written, the maximum was 4GB of PC3-8500, but with a newer Bios version, there's an improved maximum of 8GB of PC3-10600?