Well...the 89 Regency Brougham, was an excellent car. I loved the styling and the comfort to the extent, that I had it refinished at the age of eight with a color from a 98 Escort. I had it triple cleared and then I wet sanded. It was a beauty, with its Mocha Frost, pristine vinyl roof, and new chrome and grill.
It only needed a *-rack, ac comp, and water pump in its 265,000m ( near 150k with me) as I knew the previous owners.
Unfortunately, the car was hit many times, twice seriously. The final time, the insurance wanted to write it off due to miles. I re-purchased it as a salvage title, and repaired it. Hows that for devotion?
I traded it later because the interior was begining to look bad, and it was difficult to have the leather seats repaired in my area. The car was used by the dealership for one year as a "road car" racking up another 20k, after which, it was resold and is still on the road as far as I know.
The 95 Royale, also only needed minor repairs such as a rack at 120k, two wheel bearings ( one aftmkt was defective), and a rear main seal at 175k. This car was also the victim of another careless driver, although only $1400 damage at 225k. This car was a basic model, and never really was anything but extremely reliable transportation.
It was traded in April, mostly for "alienation of affection" reasons for the curent love..the LSS. The Royale has since been sold as a taxi.
Sorry for the rant... :(
Now to answer your question.
I had used wally 10w-30 synthetic on these cars...changed every 3000, since its only a Group 3, and that it is relatively cheap. I wouldnt exceed 3000m on any Group 3. The only Group 4 available over the counter is M1. I am planing on extending my drains to 4500 with this. Perhaps with a few UOA, I can extend it even further.