Using the wrong viscosity can lead to transmission slippage, overheating, or even long-term damage. This guide provides a comprehensive transmission fluid viscosity chart and explains what each rating means.
Transmission Fluid Viscosity Chart
| Transmission Fluid Type | SAE Viscosity (Cold / Hot) | Typical Application | Key Features |
|---|---|---|---|
| ATF Dexron III/Mercon | 7.5 cSt @ 100°C | Older GM, Ford, Chrysler vehicles | Multi-vehicle compatibility, good thermal stability |
| Dexron VI | 7.0 cSt @ 100°C | GM vehicles (2006+) | Low viscosity for improved fuel efficiency, better oxidation resistance |
| Mercon V | 7.0–7.5 cSt @ 100°C | Ford transmissions | Improved cold flow, extended fluid life |
| Mercon ULV (Ultra-Low Viscosity) | 5.5–6.0 cSt @ 100°C | Modern Ford, hybrid transmissions | Fuel efficiency, smooth shifting, advanced low-temp performance |
| Type F | 7.5–8.0 cSt @ 100°C | Classic Ford vehicles | High friction coefficient, older design |
| ATF T-IV / WS | 6.5–7.0 cSt @ 100°C | Toyota, Lexus | Wide temperature range, smooth shifting, extended service intervals |
| CVT Fluid NS-2 / CVT Fluid TC | 6.0–7.0 cSt @ 100°C | Nissan, Subaru CVTs | Designed for belt or chain-driven CVTs, shear-stable |
| Honda DW-1 / Z-1 CVT | 5.5–6.5 cSt @ 100°C | Honda CVTs | Low-viscosity, optimized for fuel economy and smooth CVT operation |
| Allison TES 295 / C-4 | 7.0–7.8 cSt @ 100°C | Heavy-duty trucks, buses | High thermal stability, anti-foaming, anti-wear additives |
| ZF Lifeguard 6 / 8 / 9 | 6.0–7.5 cSt @ 100°C | BMW, Audi, Mercedes-Benz | Multi-vehicle high-performance ATF, long-life fluid |
| Valvoline DEX/MERCON Equivalent | 6.5–7.5 cSt @ 100°C | Universal use | Compatible with multiple brands, oxidation resistance |
| Synthetic ATF (Multi-vehicle) | 6.0–7.5 cSt @ 100°C | Modern AT, CVT, hybrid | Superior thermal stability, long life, shear-stable |
| Toyota ATF WS (World Standard) | 6.5 cSt @ 100°C | New Toyota & Lexus ATs | Smooth shifting, enhanced durability |
| Subaru ATF-HP / ATF-iCVT | 6.0–6.5 cSt @ 100°C | Subaru CVTs | Low-viscosity, shear-stable, extended life |
| Mopar ATF+4 | 7.0 cSt @ 100°C | Chrysler, Jeep, Dodge | Extended service life, high-temp stability |
| Ford Type F Synthetic Blend | 7.5–8.0 cSt @ 100°C | Classic Ford ATs | High friction, smooth shift for older transmissions |
| Mercedes-Benz MB 236.14 / MB 236.15 | 6.5–7.5 cSt @ 100°C | Mercedes ATs | Long-life synthetic ATF, enhanced friction performance |
| BMW ATF 81 22 0 142 516 | 6.5–7.0 cSt @ 100°C | BMW automatic transmissions | High stability, low friction, extended service life |
| Volvo AW-1 / AW-55-50SN | 6.5–7.0 cSt @ 100°C | Volvo ATs | Smooth shifting, compatible with multiple Volvo models |
| Mazda ATF M-V / FZ | 6.5–7.0 cSt @ 100°C | Mazda ATs | Friction-modified for smooth engagement and durability |
| Hyundai/Kia SP-IV / SPH-IV | 6.5–7.0 cSt @ 100°C | Hyundai & Kia ATs | Low-viscosity, fuel-efficient, long-life ATF |
Notes on Viscosity Values:
The values listed in centistokes (cSt) represent fluid thickness at 100°C (212°F).
Cold viscosity (e.g., SAE J300, -40°C) is often lower for improved startup flow.
Related Transmission Fluid Level Chart(For All Types)
Why Viscosity Matters
1. Proper Lubrication
The right viscosity ensures that the moving parts of your transmission, including clutches, gears, and bearings, are well-lubricated. Fluids that are too thin may fail to protect, while fluids that are too thick can cause resistance and poor performance.
2. Shift Quality
Transmission fluids act as hydraulic media in automatic transmissions. Low-viscosity fluids help smooth shifts in cold weather, while high-viscosity fluids prevent slippage under heavy loads or high temperatures.
3. Fuel Efficiency
Modern low-viscosity fluids reduce internal drag, improving fuel economy. For instance, ULV or Dexron VI fluids are designed for newer vehicles where manufacturers aim to meet efficiency standards.
4. Longevity
Using a fluid with correct viscosity reduces wear and tear, prevents overheating, and extends the life of your transmission.
Related ULV Transmission Fluid Compatibility Chart(For All Types/Models)
How to Read Transmission Fluid Viscosity Labels
Transmission fluids are often labeled with SAE Viscosity grades or manufacturer-specific codes:
- SAE J300: Measures cold viscosity of oils. Not all ATFs are labeled this way.
- Dexron / Mercon: Proprietary fluid types with standardized performance metrics.
- CVT or Dual-Clutch fluids: Typically have specialized formulations with low viscosity to reduce slippage and improve efficiency.
Tips for Choosing Transmission Fluid
- Check the Owner’s Manual: Always follow the manufacturer’s recommended fluid type and viscosity.
- Consider Climate: Extreme cold or hot environments may require specific viscosity grades.
- Synthetic vs. Conventional: Synthetic fluids generally perform better over wide temperature ranges and last longer.
- CVT vs. Automatic vs. Manual: CVTs require special low-viscosity fluids, while manual transmissions often tolerate higher viscosities.
Common Mistakes to Avoid
- Mixing Fluids: Never mix fluids with significantly different viscosities. Even within the same brand, compatibility matters.
- Using Low-Viscosity Fluid in Older Transmissions: Older designs may require thicker fluid to maintain pressure.
- Ignoring Fluid Age: Even the correct viscosity fluid loses performance over time. Check intervals for change.
Related Allison Transmission Fluid Capacity Chart(All Models)
FAQs
What viscosity is Dexron III?
Dexron III has a viscosity of approximately 7.5 cSt at 100°C, making it slightly thicker than newer low-viscosity fluids. It is designed for older GM, Ford, and Chrysler automatic transmissions and provides good thermal stability for high-temperature operation.
How thick should transmission fluid be?
Transmission fluid thickness varies depending on the vehicle and type of transmission. Modern automatic transmissions typically use fluids in the range of 5.5–7.5 cSt at 100°C, while older transmissions may require slightly thicker fluids (7.5–8.0 cSt) to maintain proper hydraulic pressure and friction characteristics.
Is higher viscosity transmission fluid better?
Not necessarily. Higher viscosity fluid provides better protection under high loads or extreme temperatures, but it can cause sluggish shifts, reduced fuel efficiency, and poor cold-weather performance. The correct viscosity is determined by the manufacturer and is crucial for optimal transmission operation.
Is 5W-20 or 5W-30 better for older cars?
For older cars, the choice between 5W-20 and 5W-30 depends on the manufacturer’s recommendation and engine wear. 5W-30 is slightly thicker at operating temperatures, which can help older engines maintain oil pressure and reduce leaks, while 5W-20 improves fuel economy and cold-start performance.
Does higher viscosity mean more fluid?
No. Higher viscosity refers to the fluid’s thickness, not volume. Using a higher viscosity fluid does not require more fluid in the transmission; it affects how easily the fluid flows and maintains pressure within the system. Always fill to the manufacturer-specified level.
Final words
Understanding transmission fluid viscosity is essential for maintaining your vehicle’s transmission performance and longevity. Using a fluid with proper viscosity ensures smooth shifting, optimal lubrication, and protection against wear.
The table above provides a comprehensive overview of common fluids, their viscosity, and applications. Always check your vehicle manufacturer’s recommendations before topping up or changing fluid.
Choosing the right transmission fluid isn’t just about brand, it’s about viscosity, performance, and compatibility. Follow the guidelines, monitor fluid condition, and your transmission will reward you with years of reliable performance.
