Brake Fluid vs. ILSAC Standards
Comparing 2 standards across 11 specifications. 11 key differences identified.
DOT Brake Fluid (standardized under US FMVSS 116, SAE J1703/J1704, and ISO 4925) defines the hydraulic fluid specifications for automotive braking systems. Governing Dry Boiling Points (fresh fluid) and Wet Boiling Points (3.7% water contamination absorbed over time) across glycol-ether fluids (DOT 3, DOT 4, DOT 5.1) and silicone-based fluid (DOT 5).
ILSAC GF-6 (developed by the International Lubricant Standardization and Approval Committee of Japanese and American automakers) defines fuel economy, timing chain wear reduction, and engine durability standards. Splitting into GF-6A (backward-compatible for 0W-20, 5W-20, 5W-30, 10W-30) and GF-6B (dedicated to ultra-low viscosity 0W-16 oils).
Specification Comparison Table
11 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standardization
|
FMVSS 116 / SAE J1703 (DOT 3), SAE J1704 (DOT 4), ISO 4925 Class 3/4/6/7 | ILSAC GF-6A / ILSAC GF-6B (Mandated May 2020) |
|
DOT 3 Minimum Boiling Points
|
Dry: 205°C (401°F) | Wet (3.7% H₂O): 140°C (284°F) — Standard domestic vehicles | — |
|
DOT 4 Minimum Boiling Points
|
Dry: 230°C (446°F) | Wet: 155°C (311°F) — Modern European and Japanese passenger cars with ABS/ESP | — |
|
DOT 4 Class 6 (Low Viscosity)
|
Low viscosity at -40°C (max 750 mm²/s vs 1500 mm²/s standard) for rapid ABS/ESP active brake pulsing in freezing winters | — |
|
DOT 5.1 (High Performance Glycol)
|
Dry: 260°C (500°F) | Wet: 180°C (356°F) — Glycol-ether base compatible with DOT 3 and DOT 4 systems | — |
|
DOT 5 (Silicone-Based — Purple)
|
Dry: 260°C (500°F) | Hydrophobic silicone base (NEVER mix with DOT 3/4/5.1; used in classic cars and military Harley-Davidsons) | — |
|
ILSAC GF-6A (Starburst Symbol)
|
— | Backward compatible with older GF-5 and GF-4 specifications for SAE 0W-20, 5W-20, 0W-30, 5W-30, 10W-30 |
|
ILSAC GF-6B (Shield Symbol)
|
— | Exclusively for SAE 0W-16 viscosity oils (NOT backward compatible with engines requiring GF-6A / GF-5) |
|
Timing Chain Wear Test (Sequence X)
|
— | A mandatory ASTM test that limits acceptable timing chain elongation over an extended multi-day cyclic engine run (specific pass/fail thresholds are set by the ASTM Sequence X test procedure, not reproduced here in full) |
|
Piston Deposit & Cleanliness (Sequence IIIH)
|
— | A high-temperature ASTM oxidation/deposit test that runs the oil under sustained elevated temperature to evaluate resistance to ring sticking and varnish formation (exact duration/temperature are set by the ASTM Sequence IIIH test procedure) |
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Automaker Backing
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— | Alliance of Automobile Manufacturers (Ford, GM, Stellantis) and Japan Automobile Manufacturers Association (Toyota, Honda, Nissan) |