Blender running out of memory in renders, but having no problem in previews I am dealing with problem of... Out of memory in cuMemAlloc(&amp;device_pointer, size)
Even though settings are the same in render mode and preview mode I have never encountered this issue in the second one and have it all the time in the first one. 
Note I am rendering on gtx 980ti, memory Peak is usually slightly above 4000M.
If there are no fixes and you have no idea where the problem is. I at least would like to save what I see in preview mode.
preview is not the same as rendering..
you can run out of memory buy a heavier GPU card if your out of memory.
or use a renderfarm or split up the work in layer scenes