Good luck, but my experience with gear oil is that it just doesn't wash out. Time is the only real cure that I've found.
If it's any comfort, nobody is going to mistake the smell of gear oil for BO. Having worked with several people over the years who had an unnatural phobia of water and soap, I can tell you that BO strong enough to be noticed smells nothing like gear oil. If it did, it wouldn't be nearly so sickening.
Gear oil might make you smell low-class to some people, but only the truly ignorant mistake it for BO.