26-04-2020, 10:42 AM
(This post was last modified: 26-04-2020, 10:44 AM by Bob Culver.)
Hi Austin
According to graphs in the book Which Oil the crossover point for 20W/50 and 30 is far below 0C, so the multigrade does indeed incur a considerable drag penalty in normal use.
My car certainly gained performance after 20 miles or so.
Based on simple pouring viscosity 10W40 and 30 are the same at 0C. Suspect the original recommendation was to reduce leaks, quiten the rollers, and reduce follower wear prior ZDDP or equiv.
To get rid of much of the dirt (as distinct from water and acids ) the oil needs to be drained hot and the car rocked to stir it up. The impecunious can put through a filter and alternate or use as top up.
( A work colleague described tidying up his late fathers workshop. Apparently he siphoned old oil through ropes to recycle it and had quite an installation. modern additives may not make the pasage)
According to graphs in the book Which Oil the crossover point for 20W/50 and 30 is far below 0C, so the multigrade does indeed incur a considerable drag penalty in normal use.
My car certainly gained performance after 20 miles or so.
Based on simple pouring viscosity 10W40 and 30 are the same at 0C. Suspect the original recommendation was to reduce leaks, quiten the rollers, and reduce follower wear prior ZDDP or equiv.
To get rid of much of the dirt (as distinct from water and acids ) the oil needs to be drained hot and the car rocked to stir it up. The impecunious can put through a filter and alternate or use as top up.
( A work colleague described tidying up his late fathers workshop. Apparently he siphoned old oil through ropes to recycle it and had quite an installation. modern additives may not make the pasage)