I think any oil with a high TBN will help Auto-Rx in the cleaning or in the rinse cycle. I would suggest a "diesel" oil that is API rated SL/CI-4. You can find these oils in the 10W-30 or 15W-40 viscosity for conventional oil. The 10W-30 API SL/CI-4 oil variety is a little hard to find but can be found in the northern parts of the country.
I am using Auto-Rx in my wifes 1997 BMW 318i now with Amsoil XL-7500 10W-40. For the Auto-Rx rinse phase next spring I will probably use Pennzoil LongLife 15W-40.