Using the wrong weight can lead to hard shifting, overheating, sluggish performance, or even premature transmission failure.
This guide breaks down everything you need to know about transmission fluid weight, why it matters, and how to select the right one for automatic, manual, CVT, and DCT systems. A complete table of all common weight ratings is included below.
Transmission Fluid Weight
Transmission fluids weight range from low-viscosity ATFs like Dexron VI (≈6 cSt at 100°C) and Mercon ULV (≈4.5 cSt) to medium-weight options such as ATF+4 and Mercon V (≈7–7.5 cSt), along with specialized CVT fluids like Nissan NS-3 (≈5.5 cSt) and Honda HCF-2 (≈6.3 cSt).
Manual transmissions use gear-oil weights such as 70W (~4.5 cSt), 75W-90 (~14.5–15.5 cSt), and 80W-90 (~14–16 cSt), each designed to match the gearbox’s load, temperature, and performance requirements.
| Transmission Fluid Type | Type of Transmission | Actual Weight / Viscosity | Viscosity Characteristics | Typical Use Case |
|---|---|---|---|---|
| ATF Dexron II | Automatic | ~7.5 cSt at 100°C | Medium viscosity | Older automatic transmissions |
| ATF Dexron III | Automatic | ~7.0 cSt at 100°C | Medium-light | 1990s–2000s vehicles |
| ATF Dexron VI | Automatic | ~6.0 cSt at 100°C | Low viscosity | Modern GM and other vehicles |
| ATF Dexron HP | Automatic | ~5.9 cSt at 100°C | Low viscosity | GM 8-speed & 10-speed automatics |
| ATF Mercon V | Automatic | ~7.5 cSt at 100°C | Medium viscosity | Many Ford automatics |
| ATF Mercon LV | Automatic | ~6.0 cSt at 100°C | Low viscosity | Newer Ford transmissions |
| ATF Mercon ULV | Automatic | ~4.5 cSt at 100°C | Ultra-low viscosity | Ford 10R80 / 10-speed |
| ATF Mercon SP | Automatic | ~6.5 cSt at 100°C | Medium-light | 6-speed Ford transmissions |
| ATF+4 | Automatic | ~7.6 cSt at 100°C | Medium-light | Chrysler, Dodge, Jeep |
| Honda ATF DW-1 | Automatic | ~6.8 cSt at 100°C | Light viscosity | Honda/Acura automatics |
| Toyota ATF WS | Automatic | ~5.5 cSt at 100°C | Low viscosity | Toyota/Lexus automatics |
| Nissan Matic S | Automatic | ~6.9 cSt at 100°C | Medium-light | Nissan/Infiniti automatics |
| Hyundai SP-IV | Automatic | ~5.3 cSt at 100°C | Low viscosity | Hyundai/Kia 6–8-speed ATs |
| CVT Nissan NS-2 | CVT | ~6.8 cSt at 100°C | Medium-light | Older Nissan CVTs |
| CVT Nissan NS-3 | CVT | ~5.5 cSt at 100°C | Low viscosity | Modern Nissan CVTs |
| CVT Honda HCF-2 | CVT | ~6.3 cSt at 100°C | Medium-light | Honda CVTs |
| CVT Toyota FE | CVT | ~4.8 cSt at 100°C | Low viscosity | Toyota/Ken CVTs |
| CVT Mitsubishi DiaQueen J1 | CVT | ~7.0 cSt at 100°C | Medium | Mitsubishi CVTs |
| DCT Fluid 75W | Dual-Clutch | ~7.0 cSt at 100°C | Light viscosity | Dry-clutch DCTs |
| DCT Fluid 70W | Dual-Clutch | ~5.8 cSt at 100°C | Very light | Fast-shifting dry DCTs |
| DCT Fluid MTF-1 (Wet) | Dual-Clutch | ~6.5 cSt at 100°C | Medium-light | Wet-clutch DCTs |
| Ford DCT Fluid WSS-M2C200-D2 | Dual-Clutch | ~6.9 cSt at 100°C | Medium-light | Ford Powershift DCT |
| BMW DCTF-1 | Dual-Clutch | ~6.3 cSt at 100°C | Light viscosity | BMW DCT systems |
| Manual 70W | Manual | ~4.5 cSt at 100°C | Very light | Small gearboxes; cold climates |
| Manual 75W | Manual | ~5.5 cSt at 100°C | Light | Sporty small vehicles |
| Manual 75W-80 | Manual | 5.5–7.5 cSt at 100°C | Medium-light | European manual transmissions |
| Manual 75W-85 | Manual | 8.0–10.5 cSt at 100°C | Medium | Light trucks & midsize cars |
| Manual 75W-90 | Manual | 14.5–15.5 cSt at 100°C | Medium-heavy | Performance manuals |
| Manual 80W | Manual | ~10 cSt at 100°C | Medium | Medium-duty vehicles |
| Manual 80W-90 | Manual | 14–16 cSt at 100°C | Heavy | Trucks, off-road vehicles |
| Manual 85W-90 | Manual | 17–18 cSt at 100°C | Heavy | Older heavy-duty trucks |
| Manual 85W-140 | Manual/Differentials | 26–30 cSt at 100°C | Very heavy | High-load applications |
| Manual 90 (straight) | Manual | ~18 cSt at 100°C | Thick | Hot-climate heavy use |
| Manual 140 (straight) | Manual | ~30 cSt at 100°C | Very thick | Industrial & off-road |
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How to Choose the Right Transmission Fluid Weight
Choosing the correct fluid starts with one step: follow the manufacturer’s specification. Even small differences in viscosity or friction characteristics can dramatically affect transmission behavior.
1. Check the Owner’s Manual or OEM Specification
Every vehicle lists the exact fluid required, ATF type, CVT formulation, or manual transmission weight. Never substitute unless equivalent.
2. Consider Operating Conditions
Your climate and driving style may influence ideal viscosity:
- Cold climates → thinner fluids (Dexron VI, Mercon LV, 70W or 75W)
- Hot climates or heavy loads → thicker fluids (75W-90, 80W-90, ATF+4)
3. Determine Type of Transmission
- Automatic transmissions require specific ATF blends with precise friction modifiers.
- Manual transmissions rely more on gear-oil viscosity ratings.
- CVT systems are extremely sensitive; only use CVT-approved fluids.
- Dual-clutch transmissions need special DCT formulations depending on dry or wet clutch design.
4. Avoid Mixing Fluids
Mixing different weights can:
- Cause erratic shifting
- Reduce lubrication
- Damage seals
- Void warranty
Always flush and fill rather than mixing incompatible types.
Related Transmission Fluid Viscosity Chart(For All Fluid Types)
Common Symptoms of Using the Wrong Transmission Fluid Weight
Using the incorrect viscosity can create noticeable issues:
1. Hard or Delayed Shifting
Transmission may hesitate or “thud” when changing gears.
2. Overheating
Fluid too thin may cause overheating under load.
3. Slipping Gears
Fluid too thick or with incorrect friction characteristics can disrupt clutch engagement.
4. Whining or Grinding Noises
In manuals, improper weight affects gear mesh and lubrication film.
5. Reduced Fuel Efficiency
Thicker fluids increase drag, hurting fuel economy.
Fixing the issue usually requires a drain and refill with the correct fluid weight.
Related Transmission Fluid Temperature Chart(Complete Guide)
Best Practices for Maintaining Transmission Fluid Weight
1. Check Fluid Regularly
Automatic transmissions often have dipsticks, while manuals need a fill-plug inspection.
2. Replace Fluid at Recommended Intervals
Ignoring service intervals is one of the main causes of transmission wear.
3. Use Only Quality Fluids
Cheap or unapproved lubricants can shear down faster, altering viscosity out of spec.
4. Avoid Overheating the Transmission
Towing, steep terrain, or stop-and-go traffic create heat that breaks down viscosity.
5. Install an Auxiliary Cooler (if towing)
Keeps fluid weight stable under heavy strain.
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What Is Transmission Fluid Weight?
Transmission fluid weight refers to the viscosity rating of the fluid, how easily it flows at both cold and hot operating temperatures. A higher weight number generally means the fluid is thicker, while a lower number indicates it flows more easily.
- Automatic transmission fluids (ATF) typically use “multi-purpose” viscosity categories like Dexron III, Dexron VI, or Mercon V.
- Manual gearbox fluids often use gear oil ratings like 70W, 75W-80, or 80W-90.
- CVT fluids and Dual-Clutch Transmission (DCT) fluids have their own carefully engineered weights and friction properties that reduce wear and maintain smooth operation.
Choosing the wrong weight may cause improper lubrication, slipping, overheating, or stiff gear engagement.
Why Transmission Fluid Weight Matters
1. Smooth Gear Shifts
The thickness of the fluid directly affects how smoothly gears engage. Thinner fluids allow rapid shifting, while thicker fluids add resistance and cushioning.
2. Heat Management
Transmission systems create a tremendous amount of heat. Proper viscosity is essential to absorb and dissipate that heat.
3. Component Protection
Transmissions have tightly machined components, clutches, and synchronizers. Each system is designed for a specific fluid weight that ensures:
- Correct lubrication film thickness
- Stable hydraulic pressure (in automatics)
- Reliable friction levels for clutch packs
4. Fuel Efficiency
Lower-viscosity fluids reduce drag, improving fuel economy. Many modern transmissions require thinner fluids for this reason.
Related Transmission Fluid Calculator
FAQs
How much does 1 gallon of transmission fluid weigh?
One gallon of transmission fluid weighs about 7 to 7.5 pounds, depending on the brand and formulation, because ATF has a typical density of 0.85–0.90 g/cm³, which is slightly lighter than water.
What viscosity is ATF?
ATF (automatic transmission fluid) generally has a viscosity of 5–8 cSt at 100°C, with modern low-viscosity types like Dexron VI and Mercon ULV on the lower end and older fluids like Dexron III or ATF+4 on the higher end.
Are there different weights of transmission fluid?
Yes, transmission fluid comes in multiple weights and viscosity grades, including ATF types (Dexron, Mercon, ATF+4), CVT fluids, DCT fluids, and manual gear-oil weights such as 70W, 75W, 80W, 75W-90, and 80W-90, all designed for different transmission systems and load requirements.
Is water heavier than transmission fluid?
Yes, water is heavier than transmission fluid. Water weighs 8.34 pounds per gallon, while ATF weighs about 7–7.5 pounds per gallon, making transmission fluid less dense and able to float on water.
How much does 1 gallon of fluid weigh?
Most automotive fluids weigh between 6.5 and 8.5 pounds per gallon, depending on viscosity and density. For example, gasoline is around 6 lbs/gal, ATF is around 7–7.5 lbs/gal, and water is 8.34 lbs/gal.
How heavy does a transmission weigh?
A transmission typically weighs 70 to 400 pounds, depending on type: small manual transmissions start around 70–120 lbs, most automatic transmissions weigh 150–250 lbs, and heavy-duty or truck transmissions can exceed 300–400 lbs.
How much does a 5-gallon bucket of transmission fluid weigh?
A 5-gallon bucket of transmission fluid weighs about 35–38 pounds (5 gallons × ~7–7.5 lbs per gallon), not including the bucket, which may add an additional 1–2 pounds.
Final words
Transmission fluid weight is more than just a number, it’s a critical factor that determines the health, performance, and longevity of your transmission. Understanding how viscosity affects shift quality, friction, lubrication, and heat control helps you make informed maintenance decisions.
Always follow manufacturer recommendations, avoid mixing fluid types, and choose high-quality lubricants that maintain correct weight under stress. With the right fluid, your transmission will shift smoothly, stay cool, and deliver reliable performance for years.
