Steering box troubles

When I checked the oil level of the steering box of our Oval Beetle the other day, I noticed that it was almost empty. I knew that the steering box was leaking a bit, but over time, the thin oil apparently almost disappaered from it. Last time I filled the steering box, I used a special kind of oil, but I remembered reading on internet fora about filling the box with grease instead of oil and wanted to try that too. I learned however that this was done by Volkswagen from 1965 onwards. So I decided to fill it with oil again and to use transmission oil this time: 80W-90.