I heard Crucial's guarantee is that if it does not work money back but they may not have tested all ram for each Dell model. if you want to choose Crucial go for these user validated models: FYI Dell OEM 16 gb The above Dell ram is validated to run at 1600 MHz in 3847 as shown in the BIOS screenshot  
I did some upgrades to my Dell Inspiron 3847.  One of those being a ram upgrade from the basic Hynix ram it came with that was 2x4GB and ran at 1600MHz, which is the max the motherboard allowed, no problem.  I then swapped it out for Corsair Vengeance LP DDR3 1600 C10 2x8GB ram so I'd have 16GB of ram at the max speed my motherboard will allow.  However when I went into BIOS I noticed that my computer was only running it at 1333 MHz so I figured I would just turn on the XMP profile or reconfigure the ram speed.  But I went to my advanced options and as the picture below shows I only have those 3 options.  I updated my BIOS from A08 to A11 earlier today to get the newest version of the BIOS I can get but it didn't change my options available.  Is there a way to get more advanced options or do I need to change my ram that has a base clock of 1600 Mhz?[IMAGE]
My Inspiron 3847 only has 3 options in the Advanced section of my UEFI BIOS