Red Line D4 Synthetic Automatic Transmission Fluid (ATF) 1 Quart 4-Pack — Dexron/Mercon Compatible, GL-4 Gear Protection

Red Line 30504 D4 Synthetic Automatic Transmission Fluid is a versatile synthetic ATF supplied in 1‑quart bottles (4-pack) formulated to protect gears and synchromesh while improving cold-shift performance across many automatic and manual applications.

This fully synthetic transmission fluid is designed for use where Dexron III/II, Mercon/Mercon V and similar ATF specifications are recommended, and it also provides GL‑4 level protection that suits select manual transmissions and transaxles. Red Line's D4 formula blends slipperiness for smooth shifting with gear protection to meet the needs of diverse late‑model Asian and European drivetrains, and is commonly chosen by enthusiasts and technicians who want a single fluid to cover multiple service points.

Will this ATF work in my automatic transmission or power steering?

Red Line D4 is formulated to be backward compatible with many Dexron and Mercon style specifications, so it can be used in a wide range of automatic transmissions and hydraulic power steering systems that call for those fluids. Always check your vehicle's manufacturer recommendations before changing fluids.

• Compatible with Dexron III, Dexron II, Mercon, Mercon V service fills
• Suitable for many Toyota Type T‑III/T‑IV and Honda ATF‑Z1 applications
• Works in power steering systems requiring equivalent ATF grades

Can I use Red Line D4 in manual transmissions or transaxles like a T‑5 or T‑56?

Yes—unlike many ATFs, D4 offers GL‑4 level gear protection and balanced friction characteristics, making it usable in many manual transmissions, transaxles and synchromesh gearboxes that accept GL‑4 fluids. It is a popular swap for certain manual gearboxes when the manufacturer allows an ATF with GL‑4 protection.

• Commonly used in T‑5, T‑45 and T‑56 style transmissions
• Provides synchromesh-friendly friction for smoother shifts
• Delivers gear surface protection similar to traditional GL‑4 gear oils

Which vehicle makes and ATF types is Red Line D4 known to replace?

Red Line D4 is engineered to be a versatile replacement across a broad set of OEM ATF types and manufacturer designations. It is frequently selected for Asian and European makes where the listed ATF specifications are a match, helping simplify maintenance when multiple fluids are required in a shop or home garage.

• Fits Toyota Type T‑III and T‑IV service recommendations
• Compatible with Honda ATF‑Z1 and many Nissan Matic D/J/K formulations
• Works where Diamond SP‑II/SP‑III and Mazda ATF M‑V are specified
• Acceptable for many BMW, Audi and Volkswagen automatic transmissions requiring similar ATF properties

Who is this for? Red Line 30504 D4 Synthetic ATF in the 1‑quart 4‑pack targets DIY mechanics, professional technicians and enthusiasts who prefer a high‑performance, multi‑application transmission fluid. It’s particularly useful for people servicing mixed fleets or performance vehicles that need a synthetic fluid offering cold‑weather shift improvement, reliable synchro engagement and GL‑4 level gear protection. As with any fluid change, verify compatibility with your vehicle’s service manual or consult a technician to confirm suitability for your specific transmission and hydraulic systems.