Oil is viscous by nature.
The colder the oil the thicker it will be.
Hold the amps or the vials in your hand till they're the same as your body temperature. That will cause the oil to be more superfluous and therefore easier to inject.
Oil at room temperature or probably cooler depending on where you hide it can be anywhere from 70-78 degrees. Warming it to your body temperature of 98 degrees will dramatically increase the viscosity.