Cutting fence panel from bottom - will wood rot

BlueonBlue

Funny you mentioned old engine oil ...as that was exactly what we used.
It was handy we were in a hurry and no running around to buy product was needed for a cheap fence with limited life span so it didnt matter .
I cant remember but believe we coated the whole fence with it which meant it did smell oily for awhile but then was fine and cost nothing except whatever we had lying around to thin it down on the first coat.

ThisIsWeird

Hmm, it may, but it would be frowned on environmentally. And it's unlikely to take 'proper' stuff in future if you try.
You have nice-looking and solid panels there, so I'm struggling to understand your reluctance to buy proper stuff and ensure longevity.
But I still don't know what the best 'proper' stuff is!
I've just checked out no-nonsense 'wood treatment', and was disappointed to find - via the reviews - that it's only a water repellent, and contains no preservative. 
Will have another look later on. 

Elmroad82

I’m not reluctant to buy the proper stuff. I just had old oil in the garage.  I wasn’t planning on painting it all over the fence panel as it’s treated abd pre stained in brown just the bottom where the newly cut wood will sit in the gravel board. Maybe a wood preserver then add sit the fence panel in 2 shims to stop the water collecting at the base of the fence where it sits in the gravel board?