Same here, apparently the FPS on modern PC leaves much to be desired. I found some things online stating that editing the .ini file helps but all its done so far is raise the FPS to a playable degree but the graphical stuttering kinda kills the game. The only solution I have is to turn of the VSync and play with the .ini until it runs better. I know this isn't a great solution but its the best I found so far.

EDIT: I founding editing the .ini file to these appeared to fix quite a lot of the lag, however this does put more stress on your PC, however with your specs and the general lack of Oblivion's requirments you should be fine going even higher than this

uInterior Cell Buffer=32 uExterior Cell Buffer=204

Well, 6 FPS is a case for the support and not normal. If you are actually getting 6FPS in an unmodded game, I don't know what could help you, but what might help a bit otherwise are the Oblivion Stutter Remover and ENBoost.

Tried everything, nothing helps. Gonna ask for refund. Thanks anyway.