Here's a posting this year of same motor with varnish where the owner switched about at the same mileage as mh2800 to syn and reported a clean engine by 100K. If syn can do that in 40K,
HDEO can do it quicker - but I agree not in the the same 3500 mi clean/ rinse cycle of ARX.
Previous post -Had a Dodge 3.9l in a '99,1500 Ram truck, traded it in with 90,000 miles on it, got a '04 1500 Quad cab Hemi.
The first couple years I had the truck, I used a 5000 mile OCI, with what ever kind of oil and filter the people at the Goodyear Tire Store use. Then with about 50,000 miles on the engine I switched to Mobil 1, 10w-30 and I continued the 5000 mile OCIs. Mobil 1 was used for the next 10 to 20,000 miles. Then I switched to 5w-40 Shell Rotella T Full Synthetic and that is what it had in it when I traded it in.
After the first couple years of shop bulk oil, brand unknown, I did have some varnish stains on the oil cap, dip stick and the inner surfaces of the valve covers that I could see. Somewhere in the time of Mobil 1 or Rotella use this varnish dissappeared.