I seem to have misplaced my immersion condenser oil. Can you tell me what kind to purchase?

Darkfield immersion oil

We supply a bottle of microscope immersion oil with our microscopes. Microscope immersion oil is available as Type A and Type B. Type A is recommended, although either will be suitable. The difference is the viscosity of the oil. Type B as a higher viscosity and is more suitable to applications where the oil needs to cover a larger distance between the slide and lens.