I'm old enough to rememeber (Just) the launch of a World First- Duckhams Q20/50 multi valance Motor Oil! No more multiple oil changes ,one oil for all seasons. Same arguments, sucking of teeth and shaking of heads. 🤣 60 odd years later, multi valenace oil is now the norm. Transmissions and difffs I'd agree with you,
As for Halford's, no, I was using Valvolene 20/50 , which is expensive. I needed to do an oil change before going to Jersey and didn't have time to get the Valvoline so I went into Halfords and bought thier oil, which was cheaper. First thing I noticed was at the end of a long run the oil pressure stayed up compared to Valvoline. I ALWAYS let the engine idle down after a long run, since then I've used it with no problems. Maybe the long gevity of the vehicles is A they are built like bricks, B They were designed to work in extreme conditions, and C The drivers were taught to care for and be sympathtic to the vehicle. I know it's a hoary old chestnut, but Howard who was the first to teach me about mechanicals, always said 'Listen the vehicle, it will tell you if anything is wrong'.