The Rheinol Primus 5/40 is an incredible oil. I've been using it now for 7 years. I put it in my kid's and parent's 4.6 V8 Fords, in both our Honda's, in both of my 4.6 V8 Mustangs and also in the 5.4 V8 in Yellow Truck.
Before I discovered Rheinol, I was using Mobil 1 15/50 and I had good results with it. Periodic oil analytics revealed the oil was holding up well. However, when you compare the Rheinol to Mobil 1, the Rheinol is literally off the charts. It's just a better quality oil.
I changed the Mobil 1 in my Black Supercharged 2001 4.6 Mustang between 7,500 and 12,500 miles. I was rear ended and totalled-out (in the black Mustang) on the 210/I-5 connector in Sylmar on March 3, 2016.
At the time of the crash, I had 257,000 miles on the car...
I've had oil Analysis performed at both OCI's and the report revealed the oil was hiding up perfectly at 12,500 miles, with almost no detectable deterioration of VI or additives between 7,500 and 12,500 miles.
Wear metals were also extremely low in every report and I credit this to a very effective piston ring seal in the 4.6 engines (preventing hard chamber deposit migration) and a highly efficient crankcase ventilation system.
The most amazing aspect of this Rheinol is how clean it keeps the interior of an engine. Mobil 1 will tint the inside of an engine a reddish brown, but Rheinol is transparent.
TBTH, I think 5,000 miles is a good OCI (oil change interval) but with my work, I frequently passed that benchmark so often that I started going out to 7,500 or 10,000 miles between changes.
I perform oil analytics on everything, even my 1982 Honda XR500R.
I use Lucas 20/50 synthetic motorcycle oil in that, specifically formulated for the bike's wet clutch.