Okay guys this is one I can speak to from a life time of experience. A tired and worn Y block loves an oil additive that raises oil pressure. Although I've heard good things about Lucas, I always used STP engine oil additive. I built a worn out engine back in 1963 that had 100,000 miles on it. All I could afford was rings, rod and main bearings and had a machine shop grind the valves. I always added a can of STP every time I changed oil. As everyone knows, getting sufficient oil to the rocker arm shafts is in my opinion the Y blocks biggest weak point.
Sludged up oil passage ways between the cam bearing and rocker arm shafts was probably the biggest culprit back in the day. The second issue was worn cam and main bearings on high mileage engines which limited the amount of oil to the rocker arm shafts. This is where raising the oil viscosity made a big difference because it increased the oil pressure, forcing more oil up through the oil passages to the rocker arm shafts. At 200,000 miles and with the original cam bearings that 312 was still running. By then I was running 40 weight oil and STP and although there was not an abundance of oil to the rocker arm shafts, there was enough that it wasn't an issue. On a hot idling engine I could actually see the oil pressure go up 5 to 10 pounds when the STP was added. Just going to 40 weight oil helped but STP gave it added viscosity and would adhere to metal surfaces much better than oil which was especially good for cold start up's and no, I do no work for STP

Now....one word of caution if you are just trying to extend the life of the engine
I strongly recommend you drop the oil pan and clean any sludge build up from the oil pickup screen. I have seen cases where the oil pickup screen was so gunked up and restricted that the engine was starved for oil when the oil viscosity was raised. Short of a rebuild, keeping that oil pressure up and changing oil regularly will extend the life of you Y block more than anything else. I know some may not agree with my analysis on STP, but I continued to use it at every oil change even in my new cars until the close tolerance engines of recent years came out requiring 5W20 oil and I never had an engine failure.
buddy