

⚙️ Shift smarter, drive smoother — the ultimate ATF upgrade!
Castrol Transmax DEX/MERC is a premium full-synthetic automatic transmission fluid engineered with Smooth Drive Technology. It delivers superior friction durability, high-temperature oxidation resistance up to 175°C, and unmatched copper corrosion protection. Designed for both stepped and continuously variable transmissions, it supports a wide range of global vehicles, making it the go-to fluid for professional-grade transmission performance and workshop efficiency.




| ASIN | B00DILUBL6 |
| Best Sellers Rank | #13,137 in Automotive ( See Top 100 in Automotive ) #51 in Transmission Fluids |
| Brand | Castrol |
| Customer Reviews | 4.8 4.8 out of 5 stars (2,209) |
| Date First Available | July 18, 2013 |
| Global Trade Identification Number | 00079191335208 |
| Item Form | Liquid |
| Item Weight | 7.45 pounds |
| Item model number | 03520 |
| Liquid Volume | 128 Fluid Ounces |
| Manufacturer | Castrol |
| Manufacturer Part Number | 03520 |
| Material | Calcium Sulfonate, Molybdenum Disulfide |
| Model | 03520 |
| Number of Items | 1 |
| Package Information | Bottle |
| Product Dimensions | 4.62 x 9.5 x 11.52 inches |
| Recommended Uses For Product | Automotive |
| SAE J300 Viscosity Grade | 5W-30 |
| Specific Uses For Product | Automatic Transmission Maintenance, Vehicle Compatibility, Performance Improvement |
| UPC | 079191335208 |
| Unit Count | 128.0 Fluid Ounces |
| Upper Temperature Rating | 175 Degrees Celsius |
| Viscosity | 5w-30 |
W**I
Works.
Honestly can any of us really review this product? Without doing an oil analysis after thousands of miles I can’t tell you if it’s good or not. What I do trust is the brand, I know the fluid is the right spec and I liked the price. That’s what I bought it. I’m using it for DOT III power steering fluid if that matters.
C**M
great fluid
so far this is the best mercon fluid ive found, its given me the lowest trans temps of any fluid ive used in my 7.3 dually no matter what im towing
R**G
Car part
Very useful.
J**Z
Muy bueno
L**E
Price
Very reasonable priced Thank you
R**D
2005 Honda Odyssey Touring
I used this for the transmission fluid flush on my 2005 Honda Odyssey Touring with 221k miles. Unknown when last transmission fluid change was, but it's part of Honda's maintenance schedule - so ~30-60k miles. I ran this fluid for a few weeks (~500 miles) before flushing it out and putting in the Honda OEM ATF. In the Odyssey, you cannot drain all of the fluid out the first drain (some left in cooler, lines, solenoids). The recommended total "flush" is to fill/drain 3x times (I only did 2x). On the 2x fill I used the Honda OEM ATF, since the cost is reasonable for my budget. I cannot tell a difference in shifting/drive-quality between Honda OEM ATF and this.
B**O
A lot cheaper
Why did you pick this product vs others?: Works great
M**N
Proven tough through extreme personal use.
I am retired from the countries largest delivery services. I had to provide my own personal vehicle and daily my vehicle would stop and start well over 800 times. Under this punishing year round service, my transmission lasted for 13 years in one vehicle. With maintenance (change your fluids) I am convinced, from personal experienced this is the best DEX/MERC ATF fluid on the market.
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