05-06-2021, 09:43 PM
Search is going to lead many here, so;
In days of old thick oil was used to moderate consumption, leaks, and noise. Also in the absence anti wear additves (ZDTP) reduced wear of cams. (in the 1940s my very fastidious and observant father used to change main bearings about every 2 or 3 years. He reckoned the cam followers wore more on 30 than 50, not that it matters.) Anti wear additives now mean a thin oil is fine. The crossover temp where 20W50 is the same as 30 is quite low, so many Sevens work hard stirring the oil.
On early multigrades there was some question about how they behaved hot on rubbing services where it mattered, some claim a 10w30 hot behaved more as a 10 which is a bit thin.
I presume this, and the fact cars do not start off piping hot, has led to the racer boys establishing on monograde 30.
However modern multigrades and certainly the expensive and synthetic ones behave more as their rating ie 5W 30 behaves hot as 30 under stress.
For the low loadings in a stock Seven engine anything modern is more than adequate. However debate rages around the degree of detergency esp with engines not fully cleaned out and without a filter. The degree to which sediments are dislodged is a puzzle.
Note VW Beetle used no filter. Many other cars in the 50s without filters transitioned to detergent oils without wholescale troubles.
I am sceptical of classic oils. If truly so and merely API SB would be no better than the oils my father used in 1940s which resulted in 1/2 inch of grey sludge and mains rumble every 10,000 miles (lot of short runs), and rebores for all cars starting at 40,00. No one now runs sequence tests for the old API ratings. Suspect considerably exceed API SB.
In days of old thick oil was used to moderate consumption, leaks, and noise. Also in the absence anti wear additves (ZDTP) reduced wear of cams. (in the 1940s my very fastidious and observant father used to change main bearings about every 2 or 3 years. He reckoned the cam followers wore more on 30 than 50, not that it matters.) Anti wear additives now mean a thin oil is fine. The crossover temp where 20W50 is the same as 30 is quite low, so many Sevens work hard stirring the oil.
On early multigrades there was some question about how they behaved hot on rubbing services where it mattered, some claim a 10w30 hot behaved more as a 10 which is a bit thin.
I presume this, and the fact cars do not start off piping hot, has led to the racer boys establishing on monograde 30.
However modern multigrades and certainly the expensive and synthetic ones behave more as their rating ie 5W 30 behaves hot as 30 under stress.
For the low loadings in a stock Seven engine anything modern is more than adequate. However debate rages around the degree of detergency esp with engines not fully cleaned out and without a filter. The degree to which sediments are dislodged is a puzzle.
Note VW Beetle used no filter. Many other cars in the 50s without filters transitioned to detergent oils without wholescale troubles.
I am sceptical of classic oils. If truly so and merely API SB would be no better than the oils my father used in 1940s which resulted in 1/2 inch of grey sludge and mains rumble every 10,000 miles (lot of short runs), and rebores for all cars starting at 40,00. No one now runs sequence tests for the old API ratings. Suspect considerably exceed API SB.