"For some reason stuff always leaks for me at altitude. What container are you using for the olive oil?"
I use a small, lightweight nalgene type bottle with a screw top. I carry it wrapped in a small OP Aloksak, secured with a rubber band, in one of my pack's side pockets or kangaroo pouch, always straight up. It is a good idea to loosen the cap occasionally when ascending to high altitude, to avoid the problem Bob mentions.
An easier alternative is to use coconut oil, which is usually solid or semi solid at mountain temperatures and, therfore, less likely to spill. The downside is that it has a much more pronounced odor.