{"id":567,"date":"2026-08-07T12:22:15","date_gmt":"2026-08-07T04:22:15","guid":{"rendered":"https:\/\/www.katmoto.com\/?p=567"},"modified":"2026-08-12T14:59:57","modified_gmt":"2026-08-12T06:59:57","slug":"dot-3-vs-dot-4-vs-dot-5-1-brake-fluid-importer-guide","status":"publish","type":"post","link":"https:\/\/www.katmoto.com\/ja\/2026\/08\/07\/dot-3-vs-dot-4-vs-dot-5-1-brake-fluid-importer-guide\/","title":{"rendered":"DOT 3 vs DOT 4 vs DOT 5.1 Brake Fluid: An Importer\u2019s Specification and Label Checklist"},"content":{"rendered":"

Brake fluid buyers often receive the same question in three different forms: \u201cCan we replace DOT 3 with DOT 4?\u201d, \u201cIs DOT 5.1 the premium option?\u201d, or simply, \u201cWhich grade should we import?\u201d The grade number alone is not the answer. A defensible purchase starts with the vehicle maker\u2019s requirement, the applicable market standard, the fluid\u2019s test evidence, and a label that says exactly what the supplier can prove.<\/p>\n

This guide is written for automotive-parts importers, lubricant distributors, wholesalers and private-label buyers who need to compare DOT 3, DOT 4 and DOT 5.1 brake fluid without turning a technical standard into a marketing shortcut.<\/p>\n

\u4e3b\u306a\u30dd\u30a4\u30f3\u30c8\uff1a<\/strong> stock the grade required by the vehicles you actually serve. Then verify the complete specification, current technical documents, batch traceability and local label requirements. DOT 5.1 is not silicone DOT 5, and a higher number is not permission to ignore the vehicle manufacturer.<\/p>\n

DOT 3, DOT 4 and DOT 5.1 at a glance<\/h2>\n

FMVSS No. 116 sets minimum performance and labeling requirements for motor-vehicle brake fluids sold for use in the United States. The table below is a useful first screen, but it is not a substitute for reviewing the complete standard, the supplier\u2019s TDS and the intended vehicle application.<\/p>\n\n\n\n\n\n\n\n
Grade<\/th>\nFluid family<\/th>\nMinimum dry ERBP<\/th>\nMinimum wet ERBP<\/th>\nMaximum viscosity at -40\u00b0C<\/th>\nTypical buying position<\/th>\n<\/tr>\n<\/thead>\n
DOT 3<\/td>\nNon-silicone, commonly glycol-ether based<\/td>\n205\u00b0C<\/td>\n140\u00b0C<\/td>\n1,500 mm\u00b2\/s<\/td>\nEstablished passenger-car, light-commercial and hydraulic clutch applications where DOT 3 is specified<\/td>\n<\/tr>\n
DOT 4<\/td>\nNon-silicone, commonly glycol-ether\/borate-ester based<\/td>\n230\u00b0C<\/td>\n155\u00b0C<\/td>\n1,800 mm\u00b2\/s<\/td>\nBroad modern-vehicle coverage where DOT 4 is specified; exact subclass and OEM requirement still matter<\/td>\n<\/tr>\n
DOT 5.1<\/td>\nNon-silicone, commonly glycol-ether based<\/td>\n260\u00b0C<\/td>\n180\u00b0C<\/td>\n900 mm\u00b2\/s<\/td>\nHigher boiling-point and lower-temperature-viscosity applications that specifically call for DOT 5.1<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

ERBP means equilibrium reflux boiling point. \u201cDry\u201d describes new fluid under the standard test condition; \u201cwet\u201d describes fluid after a controlled water-content conditioning procedure. The wet value matters commercially because non-silicone DOT 3, DOT 4 and DOT 5.1 fluids are hygroscopic: they absorb moisture over time.<\/p>\n

First remove the biggest source of confusion: DOT 5.1 is not DOT 5<\/h2>\n

The similar names hide an important chemical difference. DOT 5 is silicone based and is identified as purple under FMVSS No. 116. DOT 5.1 is a non-silicone fluid and, like DOT 3 and DOT 4, is colorless to amber. Do not group DOT 5 and DOT 5.1 together in a catalogue, application chart or sales script. A single missing decimal point can create a serious workshop error.<\/p>\n

DOT 3, DOT 4 and DOT 5.1 fluids may be chemically compatible within the non-silicone family, but \u201ccan mix\u201d is not the same as \u201cis the correct service recommendation.\u201d Mixing changes the final fluid\u2019s performance and does not upgrade the entire system to the highest grade on the bottle. For service and stocking decisions, follow the vehicle manufacturer\u2019s specified grade and procedure.<\/p>\n

Why boiling point and low-temperature viscosity both matter<\/h2>\n

Brake fluid transmits pedal force through the hydraulic system. Under repeated braking, heat can raise fluid temperature. If the fluid boils, compressible vapor can form and pedal response may be lost. That is why buyers compare both the new-fluid dry ERBP and the wet ERBP that better represents fluid after moisture exposure.<\/p>\n

Low-temperature viscosity addresses a different problem. ABS and electronic stability-control systems modulate pressure rapidly through small passages and valves. A fluid that is too viscous in cold conditions can slow hydraulic response. DOT 5.1 has a stricter -40\u00b0C viscosity limit than the general DOT 3 and DOT 4 limits, but that does not make it a universal replacement. Some vehicle makers specify particular low-viscosity DOT 4 subclasses or proprietary requirements that must be checked separately.<\/p>\n

How an importer should choose the stocking mix<\/h2>\n

Start with applications, not with the assumption that the highest grade will sell best. Pull workshop job-card data, vehicle registration by model year, fleet maintenance requirements and distributor sell-through. For the 20\u201330 vehicle applications that generate the most brake-fluid service in your channel, record the required grade, service interval, fill volume and any named OEM specification.<\/p>\n