GTX 560 Ti Force GPU usage to 99%?

My GTX 560 Ti plays games perfectly while using 99% GPU usage. I monitor this while gaming using MSI afterburner. However, in some games like, Oblivion, it will randomly decide to use only 20% of my GPU and my frames drop from 120 to 30-40 and it starts to chug bad. It does this in several other games as well. World of Warcraft, Bioshock 2, Splinter Cell Conviction and GTA IV. Its really annoying. Is there a way to force my card to run at 99% gpu usage while i game all the time? BTW, my clock speeds are not dropping and my temps are not higher than 65c. Thanks in advance for any input.