{"product_id":"red-line-mt-90-75w-90-manual-transmission-transaxle-lubricant-1-gallon-gl-4-safe-for-brass-synchros","title":"Red Line MT-90 75W-90 Manual Transmission \u0026 Transaxle Lubricant - 1 Gallon, GL-4 Safe for Brass Synchros","description":"\u003cp\u003e\u003cstrong\u003eRed Line MT-90 75W-90 GL-4 is a manual transmission and transaxle lubricant engineered for smooth shifting, long synchro life, and protection of gear surfaces in GL-1\/GL-3\/GL-4 applications.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003eThis one-gallon manual transmission lubricant from Red Line replaces reactive sulfurs found in many hypoid oils to protect brass and bronze synchros while delivering consistent viscosity across temperature ranges. Designed for road and track use, MT-90 balances wear protection with the precise friction characteristics needed for fast, notchy-free engagement. The formula works well where special synchromesh fluids are called for and supports several motor oil equivalencies for service convenience.\u003c\/p\u003e\n\n\u003ch3\u003eHow does this oil improve shifting performance?\u003c\/h3\u003e\n\u003cp\u003eMT-90 provides a controlled coefficient of friction so synchronizers engage predictably and quietly, minimizing notchy or abrupt shifts. It is formulated to maintain that behavior from cold starts through operating temperature, which helps clutch and shift feel remain consistent.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eOptimized friction for rapid synchronizer match-up\u003c\/li\u003e\n  \u003cli\u003eStable viscosity for reliable shifts in varied temperatures\u003c\/li\u003e\n  \u003cli\u003eReduces gear and synchro wear for longer component life\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWill MT-90 harm brass or bronze synchros?\u003c\/h3\u003e\n\u003cp\u003eNo — MT-90 is safe for copper-containing synchronizer materials because it avoids the reactive sulfur chemistries common to GL-5 hypoid oils that can corrode brass and bronze. That makes it appropriate for many older and specialty transmissions specifying GL-1, GL-3, or GL-4 service levels.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eNo reactive sulfurs that attack non-ferrous metals\u003c\/li\u003e\n  \u003cli\u003eRecommended where special synchromesh fluids are requested\u003c\/li\u003e\n  \u003cli\u003eCompatible with transmissions requiring GL-4 performance\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat viscosities and applications does MT-90 cover?\u003c\/h3\u003e\n\u003cp\u003eMT-90 is a 75W-90 gear oil suitable for a broad range of manual transmissions and transaxles. It also serves as an acceptable choice in systems that call for certain SAE motor oil viscosities when used per manufacturer guidance, offering flexibility during maintenance.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003ePrimary viscosity: 75W-90 for gear protection\u003c\/li\u003e\n  \u003cli\u003eWorks in some systems where 80W, SAE 40, 10W-40, or 15W-40 guidance is present\u003c\/li\u003e\n  \u003cli\u003eUse where GL-1, GL-3, or GL-4 specifications are required\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy choose Red Line's MT-90 over other gear oils?\u003c\/h3\u003e\n\u003cp\u003eRed Line has produced performance lubricants since 1979 with a focus on engineered protection and drivetrain feel. MT-90 is formulated to deliver longer synchronizer life and dependable gear protection without sacrificing precise shift quality, making it a strong choice for both performance and daily-driven vehicles.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eHeritage brand with performance-oriented formulations\u003c\/li\u003e\n  \u003cli\u003eTargets both wear protection and shift feel simultaneously\u003c\/li\u003e\n  \u003cli\u003eCommonly chosen for classic cars, performance builds, and specialty transmissions\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWho is this for: MT-90 75W-90 GL-4 from Red Line suits technicians, enthusiasts, and fleet owners who need a transmission fluid that protects gears and synchronizers while ensuring smooth, predictable shifts. It’s particularly useful for vehicles and gearboxes that specify GL-1\/GL-3\/GL-4 service or require synchromesh-friendly fluids, including many older European and performance-oriented manual transmissions. Choose the one-gallon container for workshop convenience, frequent service intervals, or multiple-vehicle maintenance.\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 lacks reactive sulfurs found in GL-5 oils and is 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 this instead of my regular GL-5 gear oil?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Only if your transmission specifies GL-4\/GL-3\/GL-1 or special synchromesh fluids; GL-5 may be needed for hypoid differentials.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"Red Line","offers":[{"title":"Default Title","offer_id":48082861064350,"sku":"B002INX20C","price":132.5,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0781\/2041\/9486\/files\/red-line-mt-90-front-label.jpg?v=1785816871","url":"https:\/\/northtrailauto.ca\/products\/red-line-mt-90-75w-90-manual-transmission-transaxle-lubricant-1-gallon-gl-4-safe-for-brass-synchros","provider":"North Trail Auto","version":"1.0","type":"link"}