Peter
You make some valid points regards Pressure / Temperature and Viscosity.
The main piont is Longevity of Our Bristol 100D / 100D2 engines, as time goes on they show more signs of wear and spare parts become more scarce.
Most of us check for wear, whenever the engine is stripped down for regular inspection / maintenance or for more serious reasons pending the use or abuse experienced. I have found that the Millars oil has coated all wear parts very well and due to regular oil change and Filter change is far superior to the Classic Castrol Oil initially used in 2000 & 2001.
My engine when Hot runs 60/65 PSI at 3000RPM. and takes at least 8 to 10 miles of gentle motoring before I can use 3000 RPM or more.
When Cold eg Winter with outside temp of minus 5 to Zero, I tend to Run the engine at 2000RPM for 4 or 5 minutes then not exceed 2500 for at least 12 to 15 miles as the Oil pressure would try to exceed 100 PSI.
Mad Dogs and Englishmen ...... We use & enjoy our Aces, Fast, Faster and Flat out all year round as intended, after carefully running in.
Last but not Least .... Peter, Many Ace Bristol guys on this side of the pond would love to learn of a regular supply of New Old Stock Volkes Oil Filters, I haven't seen a new one for years, mind you I use Fram HP1 ( Orange ) or the smaller Mopar Black unit.So could be out of touch with the market.
Every one to their own, but seriously..... Where do you get your regular supply of new Volkes Oil Filters, The ACOC could buy say 50 or more units as initial stock for our Ace / Aceca and Greyhound owners - members.
Keith