{"id":684,"date":"2026-09-22T06:00:00","date_gmt":"2026-09-21T22:00:00","guid":{"rendered":"https:\/\/www.katmoto.com\/2026\/09\/22\/gl-4-vs-gl-5-gear-oil-importer-guide\/"},"modified":"2026-09-22T06:00:00","modified_gmt":"2026-09-21T22:00:00","slug":"gl-4-vs-gl-5-gear-oil-importer-guide","status":"publish","type":"post","link":"https:\/\/www.katmoto.com\/es\/2026\/09\/22\/gl-4-vs-gl-5-gear-oil-importer-guide\/","title":{"rendered":"API GL-4 vs GL-5 Gear Oil: A Manual Transmission and Axle Guide for Importers"},"content":{"rendered":"
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Written and technically reviewed by:<\/strong> Leo Zhuang \u2014 Automotive Lubricants Product Lead
Published:

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Quick Answer<\/h2>\n

API GL-4 and GL-5 are application and performance designations, not a simple \u201cgood versus better\u201d ranking. GL-4 is commonly associated with selected synchronized manual transmissions and moderate-duty gearing; GL-5 is primarily associated with hypoid axles working under higher sliding, shock-load and torque conditions. A GL-5 oil should not automatically replace GL-4 in a manual transmission. Importers must match the vehicle maker\u2019s API designation, SAE viscosity, synchronizer or axle design, limited-slip requirement and any formal OEM approval separately.[1]<\/a> [2]<\/a> [3]<\/a><\/sup><\/p>\n<\/section>\n

\nTable of Contents<\/strong><\/summary>\n
    \n
  1. What API GL-4 and GL-5 mean<\/a><\/li>\n
  2. GL-4 vs GL-5 comparison<\/a><\/li>\n
  3. Why GL-5 is not a universal upgrade<\/a><\/li>\n
  4. Manual transmissions and synchronizers<\/a><\/li>\n
  5. Axles, hypoid gears and limited slip<\/a><\/li>\n
  6. Seven-step selection workflow<\/a><\/li>\n
  7. Importer range and stocking plan<\/a><\/li>\n
  8. Documents and label claims<\/a><\/li>\n
  9. Common purchasing mistakes<\/a><\/li>\n
  10. B2B RFQ checklist<\/a><\/li>\n
  11. Frequently Asked Questions<\/a><\/li>\n
  12. Sources & References<\/a><\/li>\n<\/ol>\n<\/details>\n

    What API GL-4 and GL-5 actually mean<\/h2>\n

    API Publication 1560 describes automotive gear-lubricant service designations so equipment makers and users can select lubricants for manual transmissions, transaxles and axles. GL-4 and GL-5 define different service conditions and performance expectations. They do not identify base-oil type, product quality in every application or an OEM approval.[1]<\/a> [2]<\/a><\/sup><\/p>\n

    The practical distinction is the severity and type of gear service. GL-4 has long been used for spiral-bevel and selected hypoid gears under moderate conditions and for many synchronized manual transmissions where the manufacturer specifies it. GL-5 addresses severe hypoid axle service that combines high sliding with shock load, high speed or high torque. The higher extreme-pressure demand of GL-5 does not make it the correct friction system for every synchronizer.<\/p>\n

    SAE 75W-90, 80W-90 or 85W-140 answers a different question. SAE J306 classifies driveline-lubricant viscosity. A buyer must therefore verify both the SAE grade and the API service designation; neither one can substitute for the other.[3]<\/a><\/sup><\/p>\n

    GL-4 vs GL-5: purchasing comparison<\/h2>\n
    \n\n\n\n\n\n\n\n\n\n\n
    Buying question<\/th>\nAPI GL-4<\/th>\nAPI GL-5<\/th>\n<\/tr>\n<\/thead>\n
    Typical system<\/td>\nSelected synchronized manual transmissions, transaxles and moderate-duty gearing<\/td>\nHypoid drive axles, differentials and final drives under severe load<\/td>\n<\/tr>\n
    Primary performance focus<\/td>\nBalanced gear protection and transmission shift\/friction behaviour where specified<\/td>\nHigher extreme-pressure protection for severe hypoid sliding and shock load<\/td>\n<\/tr>\n
    Can it be substituted?<\/td>\nOnly if the OEM permits the exact product and viscosity<\/td>\nNot an automatic replacement for GL-4 or a dedicated MTF<\/td>\n<\/tr>\n
    Synchronizer issue<\/td>\nOften specified where synchronizer compatibility and shift quality matter<\/td>\nFormulation may not deliver the required synchronizer friction behaviour<\/td>\n<\/tr>\n
    Limited-slip issue<\/td>\nGL-4 alone does not prove LSD suitability<\/td>\nGL-5 alone does not prove LSD friction suitability<\/td>\n<\/tr>\n
    Evidence to request<\/td>\nOEM manual, exact SAE grade, product TDS and application list<\/td>\nSame evidence plus axle\/LSD and any approval verification<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

    Why GL-5 is not a universal upgrade<\/h2>\n

    The number \u201c5\u201d can mislead purchasing teams into reading GL-5 as a newer replacement for GL-4. API service designations describe applications, and the equipment specification remains controlling. A transmission designed around GL-4 may require a particular friction balance for synchronizer engagement and shift feel. A severe-duty axle may need GL-5 because hypoid tooth sliding and shock loading create a different protection requirement.<\/p>\n

    Avoid the common claim that every GL-5 product will damage yellow metals. Compatibility depends on formulation, temperature, materials and the equipment requirement. The commercially safe statement is narrower: do not substitute a GL-5 axle oil into a GL-4 manual transmission unless the OEM and product supplier explicitly support that use.<\/p>\n

    The reverse substitution is also risky. A GL-4 product should not be sold into a GL-5 hypoid axle merely because the viscosity matches. The axle may need the higher extreme-pressure performance defined for its service.<\/p>\n

    Manual transmissions: synchronizers matter<\/h2>\n

    In a synchronized manual transmission, the lubricant must protect gears and bearings while allowing the synchronizer to create controlled friction. Too much or too little friction can appear as slow engagement, baulking, notchiness or poor cold shifting. Viscosity, friction modifiers, additive chemistry and material compatibility all influence the result.<\/p>\n

    For this reason, \u201c75W-90 GL-4\u201d is still not a complete application statement. Some transmissions require a dedicated manual-transmission fluid, an OEM part number or a lower-viscosity fluid. Others permit specific GL-4 or dual-rated products. The product TDS should name the intended applications and exclusions; a generic GL number on the front label is not enough.<\/p>\n

    Importers should build a fitment record by transmission family, vehicle market and model year. Do not convert an unverified global cross-reference into a sales promise.<\/p>\n

    \"KATMOTO
    KATMOTO gear-oil packaging. Confirm API service designation, SAE grade and axle application independently.<\/figcaption><\/figure>\n

    Axles, hypoid gears and limited-slip differentials<\/h2>\n

    Hypoid final drives use offset gear geometry with substantial sliding. Under high torque, shock load or high speed, the oil must maintain protection at the tooth contact. This is the central market for GL-5-type extreme-pressure axle oils described by API Publication 1560.<\/p>\n

    KATMOTO GEAR EP 80W-90<\/strong><\/a> and KATMOTO GEAR EP 85W-140<\/strong><\/a> are positioned as API GL-5 extreme-pressure gear oils for drive axles, differentials and final drives where the corresponding SAE grade and performance level are specified. Their product pages distinguish \u201csuitable for\u201d wording from formal approval and instruct users to follow the OEM manual.[6]<\/a> [7]<\/a><\/sup><\/p>\n

    Limited-slip is a separate check. A clutch-type LSD may require controlled friction or an LS-specific fluid; an open differential does not. ZF\u2019s official lubricant lists illustrate how axle families and lubricant classes are separated. If approval is claimed, verify it in the current official list rather than treating a supplier statement as proof.[4]<\/a> [5]<\/a><\/sup><\/p>\n

    \"KATMOTO
    Pack size does not change fitment: each SKU still needs a matched TDS, label and application record.<\/figcaption><\/figure>\n

    Seven-step gear-oil selection workflow<\/h2>\n
      \n
    1. Record the vehicle, model year, market version, transmission or axle code and service duty.<\/li>\n
    2. Read the OEM manual for the exact API designation, SAE viscosity and any part number or approval.<\/li>\n
    3. Identify whether the unit is a synchronized manual transmission, transaxle, transfer case, open axle, locking axle or limited-slip differential.<\/li>\n
    4. Check ambient temperature, towing, shock load, off-road use and drain interval without using duty as permission to override the OEM grade.<\/li>\n
    5. Compare the exact product TDS, applications and exclusions with the equipment requirement.<\/li>\n
    6. Verify any \u201capproved\u201d claim in the current OEM or component-maker list; keep \u201cmeets\u201d and \u201csuitable for\u201d wording distinct.<\/li>\n
    7. Save the fitment source, TDS revision, label revision, SKU and responsible approver, then recheck after any change.<\/li>\n<\/ol>\n

      Importer range and stocking plan<\/h2>\n
      \n\n\n\n\n\n\n\n\n
      Range position<\/th>\nTypical demand<\/th>\nRequired control<\/th>\nDo not assume<\/th>\n<\/tr>\n<\/thead>\n
      GL-4 \/ dedicated MTF<\/td>\nSynchronized manual transmissions and transaxles<\/td>\nTransmission-specific fitment and shift-performance evidence<\/td>\nOne GL-4 grade covers every manual gearbox<\/td>\n<\/tr>\n
      GL-5 SAE 80W-90<\/td>\nCommercial, construction and mining axles where specified<\/td>\nAxle specification, climate and application list<\/td>\nIt can replace every 75W-90 or GL-4 fluid<\/td>\n<\/tr>\n
      GL-5 SAE 85W-140<\/td>\nHot-climate, heavy-load and severe-duty axles where specified<\/td>\nMeasured market demand and OEM grade confirmation<\/td>\nThicker oil is a universal upgrade<\/td>\n<\/tr>\n
      GL-5 LS product<\/td>\nClutch-type limited-slip differentials where specified<\/td>\nLSD design and friction requirement<\/td>\nEvery GL-5 product is LS-compatible<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

      Stock from the destination market\u2019s actual vehicle parc and workshop demand. Record rejected fitments and lost enquiries before adding another viscosity or performance tier. A smaller range with reliable application data is safer than a wide catalogue built from copied cross-references.<\/p>\n

      Documents and label claims to verify<\/h2>\n

      Request a current TDS and SDS for the exact quoted product. The TDS should identify SAE grade, performance wording, applications, exclusions and key physical properties. The SDS is a safety and transport document; it does not prove fitment.<\/p>\n

      Align the quotation, product code, TDS, label, carton and invoice. Distinguish \u201cAPI GL-5,\u201d \u201cmeets performance requirements,\u201d \u201csuitable for use\u201d and \u201cofficially approved.\u201d An OEM name in a marketing table is not automatically an approval.<\/p>\n

      Verify batch coding, closure and leakage checks, retained samples, destination-language warnings and supplier change notification before shipment. A formula or claim change should trigger document and fitment reapproval.<\/p>\n

      Common purchasing mistakes<\/h2>\n