Overview
CF-4 20W-50 is a heavy-duty diesel engine oil in the SAE 20W-50 viscosity grade, formulated to API CF-4. API now lists CF-4 as obsolete: it is not suitable for most diesel automotive engines built after 2009, and remains relevant to older engines whose manuals specify it.
The specification table publishes typical values from the product data sheet, each with its ASTM method: kinematic viscosity at 40 °C and 100 °C, cold-cranking viscosity, base number, Noack volatility and foaming tendency, plus viscosity after shear and copper corrosion. Check those values and the API category against the engine manufacturer's requirement before ordering.
Application
Older diesel engines specified for CF-4
Engines and fleets whose service manuals name API CF-4, typically equipment built before the later diesel categories were introduced.
Application
Operating climate suited to SAE 20W-50
Cold-start performance is rated at -15 °C under SAE J300; choose this grade where ambient temperatures and the manufacturer's viscosity chart allow 20W-50.
Feature
Inside the SAE J300 limits for 20W-50
Kinematic viscosity at 100 °C is 19.5 cSt, within the SAE J300 band for grade 50 (16.3 to below 21.9 cSt). Cold-cranking viscosity is 8,980 cP at -15 °C, under the 9,500 cP maximum that SAE J300 sets for 20W.
Feature
Base number 11 mg KOH/g
The total base number (TBN, ASTM D2896) of 11 mg KOH/g is the oil's alkaline reserve for neutralising acidic combustion by-products between drains.
Feature
Viscosity index 132, Noack 6.5 %wt
A viscosity index of 132 (ASTM D2270), Noack evaporation loss of 6.5 %wt (ASTM D5800) and a pour point of -24 °C (ASTM D97) are published as typical values.
