Overview
SN 10W-40 is a synthetic-based gasoline engine oil for passenger cars in the SAE 10W-40 viscosity grade, formulated to API SN. API lists SN as a current category for gasoline automotive engines of model year 2020 and older.
The specification table publishes typical values with their ASTM methods — kinematic viscosity, cold-cranking viscosity, Noack volatility, base number, shear stability, foaming tendency and copper corrosion — so the oil can be checked against the vehicle handbook before purchase.
Application
Gasoline passenger-car engines
Vehicles whose handbook calls for API SN — per API, gasoline engines of model year 2020 and older — or an earlier API gasoline category.
Application
Climates suited to SAE 10W-40
The 10W winter rating is tested at -25 °C under SAE J300; use this grade where the handbook's viscosity chart allows 10W-40 for local temperatures.
Feature
Inside the SAE J300 limits for 10W-40
Kinematic viscosity at 100 °C is 15.3 cSt, within the SAE J300 band for grade 40 (12.5 to below 16.3 cSt). Cold-cranking viscosity is 4,691 cP at -25 °C, under the 7,000 cP maximum that SAE J300 sets for 10W.
Feature
Viscosity index 146, Noack 4.3 %wt
A viscosity index of 146 (ASTM D2270), Noack evaporation loss of 4.3 %wt (ASTM D5800) and a pour point of -30 °C (ASTM D97) are published as typical values.
Feature
Base number 6.05 mg KOH/g
The total base number (TBN, ASTM D2896) of 6.05 mg KOH/g is the oil's alkaline reserve for neutralising acidic combustion by-products between drains.
