Short answer
ASTM D3306 is the standard specification for glycol-based engine coolant in automobiles and other light-duty service. ASTM D6210 covers fully formulated glycol coolant for heavy-duty engines, and ASTM D4985 covers low-silicate heavy-duty coolant that needs an initial charge of supplemental coolant additive. A coolant that lists one of these is stating it was formulated to that specification.
ASTM D3306: light-duty coolant
D3306 covers ethylene glycol, propylene glycol and glycerin-containing coolants for passenger cars and light-duty systems. Current editions describe concentrates (Types I, II and V) meant to be mixed with water, normally at 40 to 60 percent by volume, and prediluted versions (Types III, IV and VI) that are at least 50 percent concentrate.
The specification sets physical and chemical limits plus corrosion and compatibility tests aimed at the metals and materials in automotive cooling systems. It does not prescribe one inhibitor chemistry, so both conventional and extended-life coolants can be written to it.
ASTM D6210: fully formulated heavy-duty coolant
D6210 is for heavy-duty engines, including on-highway trucks and off-road equipment. It covers coolants made from virgin or recycled ethylene or propylene glycol, used at 40 to 60 percent concentrate or as a 50 percent minimum predilute, to protect against corrosion, cavitation, freezing and boiling.
“Fully formulated” means the coolant is designed to go into the engine without a separate supplemental coolant additive at initial fill; maintenance additions are then made according to the engine maker’s instructions.
ASTM D4985: low-silicate coolant plus SCA
D4985 covers low-silicate ethylene glycol coolant for heavy-duty service. Coolant meeting it requires an initial charge of supplemental coolant additive and regular maintenance doses, particularly in engines with wet cylinder liners. The engine or vehicle maker sets the dosing; without guidance, the SCA supplier’s instructions apply.
Reading the label against your manual
Engine makers often require their own coolant specification in addition to, or instead of, an ASTM standard, and some limit chemistry such as nitrite, silicate or phosphate content. Check the manual first, then confirm the coolant names that requirement.
Mix concentrate with distilled or deionized water unless the coolant is a predilute; hard water minerals can drop out as scale. Freeze point, pH and inhibitor levels can be checked with test strips or a coolant analysis.
Frequently asked questions
Can I use D3306 coolant in a heavy-duty diesel?
Only if the engine maker allows it. Heavy-duty engines are typically specified with D6210 or D4985 coolant, or an OEM heavy-duty specification, because of liner cavitation protection.
Does D3306 cover propylene glycol coolant?
Current editions of D3306 include propylene glycol coolant types alongside ethylene glycol and glycerin-containing types.
General maintenance information. Always follow your vehicle or equipment manufacturer’s requirements and the current product data. Questions? Email [email protected].
