{"product_id":"redline-oil-mt-90-75w-90-gl-4-manual-transmission-fluid-1-quart-synchro-safe-smooth-shifting","title":"Redline Oil MT-90 75W-90 GL-4 Manual Transmission Fluid — 1 Quart, Synchro-Safe Smooth Shifting","description":"\u003cp\u003e\u003cstrong\u003eRed Line MT-90 75W-90 GL-4 is a high-performance manual transmission and transaxle lubricant engineered to protect gears and synchronizers while delivering smooth, sure shifts.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003eThis 1-quart Red Line formulation is designed for manual gearboxes and transaxles that specify GL-4 service and 75W-90 viscosity. It provides a balance of wear protection, friction control for synchronizers, and thermal stability for a wide variety of passenger cars, sport compacts, and light trucks. Because it avoids the aggressive sulfur additives found in many GL-5 fluids, MT-90 is safe for bronze and brass synchros while still giving robust gear protection.\u003c\/p\u003e\n\n\u003ch3\u003eHow does MT-90 improve shifting performance?\u003c\/h3\u003e\n\u003cp\u003eMT-90 has a tuned friction characteristic that reduces notchy or grinding shifts and helps synchronizers match speeds quickly. The lubricant remains stable when cold, so shifts feel consistent from startup through operating temperature.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eOptimized coefficient of friction for smooth synchro engagement\u003c\/li\u003e\n  \u003cli\u003eStable low-temperature fluidity for predictable cold shifts\u003c\/li\u003e\n  \u003cli\u003eConsistent shift feel under repeated use\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWill this oil protect my gears and synchronizers?\u003c\/h3\u003e\n\u003cp\u003eYes — MT-90 combines wear-reducing additives with a GL-4 formulation that is compatible with yellow metals used in synchronizers. It reduces wear on gear teeth and extends synchronizer life compared with oils that lack proper friction modifiers or use reactive sulfur compounds.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eGL-4-rated additives for gear surface protection\u003c\/li\u003e\n  \u003cli\u003eNo reactive sulfurs that harm brass or bronze synchros\u003c\/li\u003e\n  \u003cli\u003eFormulation focused on longer component life\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhich vehicles and service specifications are appropriate for this oil?\u003c\/h3\u003e\n\u003cp\u003eMT-90 is intended for manual transmissions and transaxles specifying GL-1, GL-3, or GL-4 service and a 75W-90 viscosity. It also works where OEMs call for special synchromesh fluids or when compatibility with brass synchros is required.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eSuitable for many passenger cars, sport compacts, and light trucks\u003c\/li\u003e\n  \u003cli\u003eCompatible with GL-1, GL-3, and GL-4 service requirements\u003c\/li\u003e\n  \u003cli\u003eCan replace many special synchromesh fluids in OEM specifications\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow should I choose between MT-90 and other gear oils?\u003c\/h3\u003e\n\u003cp\u003eChoose MT-90 when the gearbox specification calls for GL-4 service or when synchro compatibility with yellow metals is important. Avoid GL-5-only oils in these applications because they commonly contain sulfur compounds that can damage brass and bronze components.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003ePick MT-90 for GL-4 or synchromesh-specified gearboxes\u003c\/li\u003e\n  \u003cli\u003ePrefer it where brass\/bronze synchros are present\u003c\/li\u003e\n  \u003cli\u003eConsult the vehicle manual when in doubt about viscosity and spec\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWho is this for? Red Line MT-90 75W-90 is aimed at drivers, technicians, and restoration enthusiasts who need reliable manual transmission protection without sacrificing smooth shifting. It is well suited for performance-minded owners, classic car restorations where brass\/bronze synchros must be preserved, and any service bay replacing or topping off gear oil in GL-4 applications. Use it when your owner's manual or transaxle plate specifies GL-4 or a 75W viscosity, or when better synchronizer life and consistent shift quality are priorities.\u003c\/p\u003e\n\u003csection class=\"product-faq-snippet\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Is MT-90 safe for brass synchronizers?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Yes. MT-90 is a GL-4 formulation that avoids reactive sulfurs, making it safe for brass and bronze synchronizers.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Can I use MT-90 in gearboxes requiring GL-5?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: No. MT-90 is formulated for GL-4 service; GL-5 oils contain additives that can harm yellow metals and alter synchro function.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"Redline Oil","offers":[{"title":"Default Title","offer_id":48087364436126,"sku":"B000CPCBEQ","price":33.48,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0781\/2041\/9486\/files\/red-line-mt-90-front-quart-bottle.jpg?v=1785921818","url":"https:\/\/northtrailauto.ca\/products\/redline-oil-mt-90-75w-90-gl-4-manual-transmission-fluid-1-quart-synchro-safe-smooth-shifting","provider":"North Trail Auto","version":"1.0","type":"link"}