With all the emphasis for resource conserving (understood that 10w-40 is not exactly resource conserving), why would SOPUS 10w-40 class oils get thicker when transition from SM to SN? Was SM perhaps too light w/ observable consequences being reported? Were the SL oils as light as SM, but with higher levels of plating additives? Are the SN formulations are nearly in the 15w-40 range to compensate for lower levels plating metals relying more on film thickness? Couple of comparisons below:
PYB SM ..............PYB SN
KV40 = 96.9 .........KV40 = 104.7
KV100 = 14.0 ........KV100 = 15.5
HTHS = 3.7 ..........HTHS = 3.8
Pour Point = -30 ....Pour Point = -42
Shell Formula has a similar viscosity increase in the 10% range along with the same 10-15 degree lowering of the pour point. Values are nearly identical to PYB. Quaker State however, looks as though they did not change the formuation from SM to SN.
PYB SM ..............PYB SN
KV40 = 96.9 .........KV40 = 104.7
KV100 = 14.0 ........KV100 = 15.5
HTHS = 3.7 ..........HTHS = 3.8
Pour Point = -30 ....Pour Point = -42
Shell Formula has a similar viscosity increase in the 10% range along with the same 10-15 degree lowering of the pour point. Values are nearly identical to PYB. Quaker State however, looks as though they did not change the formuation from SM to SN.