Engine Coolant & Antifreeze vs. Automatic Transmission Fluids (ATF)
Comparing 2 standards across 14 specifications. 14 key differences identified.
Automotive Engine Coolant (standardized under ASTM D3306 and SAE J1034) consists of an ethylene glycol (or propylene glycol) base mixed 50/50 with demineralized water and specialized corrosion inhibitor additive packages. Dividing into classical IAT (Inorganic Acid), modern OAT (Organic Acid Technology / Long Life), and HOAT (Hybrid OAT with silicates/phosphates).
Automatic transmission fluids (ATF) are highly engineered multi-functional hydraulic fluids standardized by OEM specifications (GM Dexron VI, Ford Mercon LV, Chrysler ATF+4, Toyota WS, ZF Lifeguard) into stepped planetary, Continuously Variable (CVT), and Dual-Clutch (DCT) fluid formulations with strict kinematic viscosities and friction-modifier curves.
Specification Comparison Table
14 Parameters| Parameter / Spec | ||
|---|---|---|
|
Base Liquid Mixture
|
50/50 mix of Ethylene Glycol and pure demineralized water (Freeze point: -37°C / -34°F; Boil point: 108°C / 226°F at 1 atm, 129°C / 265°F under 15 psi cap) | — |
|
IAT (Inorganic Acid Technology — Green)
|
Silicate and phosphate inhibitors (2-year / 30,000-mile service life; standard on pre-2000 vehicles with cast-iron blocks and copper radiators) | — |
|
OAT (Organic Acid Technology — Orange/Pink)
|
Carboxylate-based inhibitors (5-year / 150,000-mile long-life; GM Dex-Cool, VW G12/G12+, Toyota Super Long Life, Ford Orange) | — |
|
Si-OAT / HOAT (Hybrid OAT — Violet/Blue/Yellow)
|
Combines organic acids with low-depletion silicates or phosphates (VW G13/G12evo, Mercedes MB 325.5, BMW Blue/Magenta, Asian P-HOAT) | — |
|
Asian P-HOAT (Phosphated HOAT — Pink/Blue)
|
Uses phosphates instead of silicates (Toyota, Honda, Nissan, Subaru, Hyundai/Kia strictly forbid silicates due to water pump seal erosion) | — |
|
European Si-HOAT (Silicated HOAT)
|
Uses silicates instead of phosphates (European water has high calcium hardness; phosphates create calcium phosphate scale deposits) | — |
|
Governing Standards
|
— | SAE J311 / GM GMN10060 (Dexron VI) / Ford WSS-M2C938-A (Mercon LV) / JASO 1-A-LV (Japanese OEM) |
|
GM Dexron VI
|
— | Viscosity: 5.83 cSt at 100°C | Fully backward compatible with Dexron II/III | Shear-stable synthetic |
|
Ford Mercon LV
|
— | Viscosity: 5.7 cSt at 100°C | Low-viscosity standard for modern 6-speed and 10-speed (10R80) transmissions |
|
Chrysler / Stellantis ATF+4
|
— | Viscosity: 7.3 cSt at 100°C | High shear-stability Group III synthetic | Mandatory for Torqueflite / 42RLE |
|
Toyota Genuine ATF WS
|
— | Viscosity: 5.4 cSt at 100°C | Low-viscosity 'World Standard' for Toyota/Lexus 6/8-speed automatic transmissions |
|
CVT Fluid (Push-Belt / Chain)
|
— | High metal-to-metal steel belt friction coefficients (NS-2/NS-3, Lineartronic) | NEVER mix with standard ATF |
|
Dual-Clutch Transmission (DCT/DSG)
|
— | Wet-clutch synchronization + high-pressure hydraulic valve bodies (VW G 052 182 / Pentosin FFL-2) |
|
Operating Temperature Limits
|
— | Optimal: 77°C–93°C (170°F–200°F) | Every 11°C (20°F) above 93°C halves fluid life via thermal oxidation |