Castrol Transmission Fluid Guide: DEXRON, MERCON, CVT, Type F & TES 668
By on Sep 28 2026
Choosing transmission fluid is not as simple as picking any automatic transmission fluid off the shelf. Different transmission designs require specific friction characteristics, viscosities, additive systems, and manufacturer specifications. Selecting a fluid that matches those requirements is an important part of proper transmission service.
The best place to start is your vehicle or equipment owner's manual. Look for the exact transmission fluid specification required, then compare that requirement with the approvals and recommended applications of the fluid you are considering.
Petroleum Service Company carries several Castrol transmission fluids for passenger vehicles, imported vehicles, continuously variable transmissions, older Ford applications, and Allison heavy-duty automatic transmissions. This guide explains where each product fits and what to check before purchasing.
What Transmission Fluid Do I Need?
Transmission fluid should be selected by specification and application, not simply by brand, color, or whether the container says ATF.
Depending on the transmission, you may see requirements such as:
- DEXRON
- MERCON
- Type F
- JASO performance requirements
- Manufacturer-specific ATF specifications
- CVT fluid requirements
- Allison TES specifications
Before purchasing transmission fluid, confirm the transmission type, vehicle or equipment model and year, and exact fluid specification required by the manufacturer.
Castrol Transmission Fluids Available from PSC
| Castrol Product | Best Starting Point | General Application |
|---|---|---|
| Castrol Transmax DEX/MERC ATF | Older GM and Ford vehicles | Applications requiring older DEXRON and MERCON fluids |
| Castrol Transmax DEXRON VI / MERCON LV ATF | Newer GM and Ford applications | DEXRON VI and MERCON LV requirements |
| Castrol Transmax Import Multi-Vehicle ATF | Many Asian and imported vehicles | Selected Honda, Toyota, Nissan and other import applications |
| Castrol Transmax ATF/CVT Universal | Multi-vehicle ATF and selected CVT applications | Selected conventional automatic transmissions and CVTs |
| Castrol Transmax Type F ATF | Older Ford applications | Applications specifically requiring Type F |
| Castrol TranSynd 668 | Allison heavy-duty automatic transmissions | Allison TES 668 applications |
This chart is intended as a starting point. Always confirm the product's current application information against the transmission manufacturer's requirements.
Castrol Transmax DEX/MERC ATF
Shop Castrol Transmax DEX/MERC ATF →
Castrol Transmax DEX/MERC is intended primarily for older automatic transmissions requiring legacy DEXRON or MERCON-type fluids.
It is a logical starting point when the vehicle or equipment documentation calls for an older specification such as DEXRON III or MERCON.
Do not assume DEX/MERC is appropriate for transmissions requiring newer specifications such as DEXRON VI or MERCON LV. Those requirements should be matched with an appropriate newer fluid.
Castrol Transmax DEXRON VI / MERCON LV ATF
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Castrol Transmax DEXRON VI / MERCON LV is designed for applicable General Motors and Ford automatic transmissions requiring these newer fluid specifications.
What is DEXRON VI?
DEXRON VI is a General Motors automatic transmission fluid specification used in many newer GM applications. It succeeded several earlier DEXRON specifications for appropriate transmissions.
What is MERCON LV?
MERCON LV is a Ford automatic transmission fluid specification. The LV designation refers to a lower-viscosity formulation required by applicable Ford transmissions.
A fluid carrying both applications can simplify product selection, but the transmission's required specification should still be verified before use.
Castrol Transmax Import Multi-Vehicle ATF
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Castrol Transmax Import Multi-Vehicle is formulated for use in many Asian and imported vehicle automatic transmissions.
It may be appropriate for selected Honda, Toyota, Nissan, Hyundai, Lexus, Mazda, Mitsubishi, and other applications covered by Castrol's application guidance.
When should I consider an import multi-vehicle ATF?
This type of fluid can be useful when servicing an imported vehicle that requires one of the specifications listed in the product's application guide.
However, multi-vehicle does not mean universal. Some manufacturers use multiple transmission designs and fluid specifications across their vehicle lineups.
Always verify the exact transmission and required fluid before purchasing.
Castrol Transmax ATF/CVT Universal
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Castrol Transmax ATF/CVT Universal is formulated for a broad range of selected conventional automatic transmissions and continuously variable transmissions.
This makes it one of the more versatile transmission fluids in PSC's Castrol assortment, but its broad application range should not be interpreted to mean it can be used in every automatic transmission or CVT.
Is CVT Fluid the Same as Regular Automatic Transmission Fluid?
Not necessarily.
A continuously variable transmission operates differently from a conventional stepped automatic transmission and may require a fluid with specific friction and performance characteristics.
A conventional ATF should therefore not be assumed to work in a CVT simply because both are automatic transmissions.
Castrol Transmax ATF/CVT Universal is formulated for selected applications across both transmission types. Before using it, confirm that your transmission and required specification are included in the current Castrol application guidance.
What Does "Suitable for Use" Mean?
Transmission fluid product literature may distinguish between an OEM approval and a manufacturer's suitable-for-use recommendation.
An OEM-approved fluid has gone through the applicable manufacturer's approval process for that specification.
A suitable-for-use recommendation indicates that the lubricant manufacturer considers the product appropriate for the listed application based on testing, formulation knowledge, and technical evaluation.
These designations are useful, but they are not identical. Check the product documentation if an OEM approval is specifically required.
Castrol Transmax Type F ATF
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Type F transmission fluid is primarily associated with older Ford automatic transmissions and certain specialty applications requiring Type F friction characteristics.
Castrol Transmax Type F is intended for applications specifically calling for Type F or the Ford specifications listed for the product.
Can I use Type F instead of DEXRON or MERCON?
Not simply because all three are automatic transmission fluids.
Type F has different friction characteristics from fluids designed around DEXRON or MERCON specifications. Use Type F only where the vehicle, transmission, or equipment manufacturer calls for that fluid type.
Castrol TranSynd 668 for Allison Transmissions
Castrol TranSynd 668 serves a different application segment from the passenger-vehicle Transmax products.
It is a full-synthetic automatic transmission fluid formulated for Allison heavy-duty on-highway automatic transmissions requiring the TES 668 specification.
Castrol identifies TranSynd 668 as:
- Allison TES 668 approved
- Backward compatible with applicable TES 295 applications
- Backward compatible with applicable TES 468 applications
- Not approved for Allison TC10 transmissions
What is Allison TES 668?
TES 668 is an Allison Transmission fluid specification that follows the earlier TES 295 specification and establishes performance requirements for applicable Allison automatic transmissions.
Fleet operators and maintenance professionals should confirm the required Allison specification before choosing a transmission fluid.
DEXRON vs. MERCON: Are They the Same?
No. DEXRON and MERCON are separate automatic transmission fluid specification families.
DEXRON specifications originated with General Motors.
MERCON specifications originated with Ford.
Some transmission fluids are formulated for applications across both specification families, but that does not make every DEXRON and MERCON fluid interchangeable.
For example:
- Transmax DEX/MERC targets older DEXRON and MERCON applications.
- Transmax DEXRON VI / MERCON LV targets newer DEXRON VI and MERCON LV requirements.
The exact specification is more important than simply seeing the DEXRON or MERCON name.
How to Choose the Right Castrol Transmission Fluid
Identify the transmission type
Determine whether the vehicle uses a conventional automatic transmission, continuously variable transmission, Allison heavy-duty automatic transmission, or another specialized design.
Find the required fluid specification
Check the owner's manual, service manual, transmission identification information, or manufacturer documentation.
Look for requirements such as DEXRON VI, MERCON LV, Type F, TES 668, or another manufacturer-specific specification.
Match the requirement to the Castrol product
Compare the required specification with the current Castrol product data sheet or application guide.
Do not select a fluid based only on the product family or brand name.
Check whether approval is required
Some applications specifically require an OEM-approved fluid. Others may permit fluids identified by the lubricant manufacturer as suitable for use.
Verify which type of qualification your transmission requires.
Be cautious when switching or mixing fluids
Different transmission fluids can use different base oils, additive systems, viscosities, and friction characteristics.
When changing fluid types, follow the vehicle or transmission manufacturer's service procedure and the lubricant manufacturer's recommendations. If the existing fluid is unknown, confirm compatibility before mixing products.
Quick Castrol Transmission Fluid Selector
The vehicle or transmission manufacturer's specification remains the deciding factor.
Frequently Asked Questions
Shop Castrol Transmission Fluids at PSC
Petroleum Service Company carries Castrol transmission fluids for passenger vehicles, imported automobiles, CVTs, older Ford applications, and Allison-equipped commercial vehicles.
Before ordering, confirm the exact fluid specification required by the vehicle or transmission manufacturer and review the current Castrol product information for the fluid you are considering.
Browse Castrol Fluids at PSC
