By Travis Knappett, Kompo® Oil & Grease Specialist
When it comes to machinery lubrication, workshop maintenance, or selecting the right hydraulic fluid, it’s important to know:
“What is ATF, and can I use it as hydraulic oil?”
Choosing the wrong fluid can cause premature wear, seal damage, and even complete hydraulic failure. As one of the UK’s leading suppliers of oils, lubricants, and spares for plant machinery, here at HTS Spares, we want operators and mechanics to make the safest and most cost-effective choice.
Below, I break down exactly what ATF is, how it differs from hydraulic oil, and when/if you can safely use one in place of the other.
What Is ATF (Automatic Transmission Fluid)?
Automatic Transmission Fluid (ATF) is a specialised lubricant designed for use inside automatic gearboxes, power steering systems, and certain hydraulic-assisted automotive components. Unlike standard hydraulic oils, ATF is formulated with:
- Friction modifiers (to manage clutch engagement)
- Detergents and dispersants (to keep internal components clean)
- Anti-wear and anti-foam additives
- High viscosity stability across temperature extremes
- Bright red dye (for easy leak identification)
Because automatic transmissions rely on fluid friction, the additives in ATF are engineered to provide precise frictional characteristics - something ordinary hydraulic oil doesn’t need.
What Is Hydraulic Oil?
Hydraulic oil is a non-compressible fluid used to transfer power in hydraulic systems, including:
- Excavators
- Telehandlers
- Forklifts
- Loaders
- Hydraulic rams and pumps
Hydraulic oils such as ISO 32, ISO 46, and ISO 68 contain additives tailored for:
- Wear protection
- Thermal stability
- Water separation
- Oxidation resistance
- Anti-foaming
- Rust and corrosion protection
Unlike ATF, hydraulic oil is not formulated to control friction, its primary job is to transmit power smoothly and efficiently.
Can ATF Be Used as a Hydraulic Oil?
Sometimes - but not usually in construction machinery.
And only if the manufacturer specifically allows it.
Some hydraulic systems, particularly in older tractors, power steering systems, and automotive-grade hydraulic components, are designed to use ATF because they require friction-modified fluid. However, in the world of construction machinery, plant equipment, agricultural machinery, access platforms, and industrial hydraulics, ATF is usually not suitable and can lead to:
- Seal swelling or degradation
- Overheating
- Premature pump wear
- Incorrect hydraulic response
- System noise and cavitation
- Lubrication failure under load
The safest rule of thumb we use at HTS Spares is simple:
Only use ATF in a hydraulic system if the equipment manufacturer specifically states that ATF is compatible.
If you're working on construction plant such as JCB, CAT, Kubota, Manitou, Bobcat, etc., these machines almost always require ISO-grade hydraulic oil, not ATF.
ATF vs Hydraulic Oil: Key Differences
| Property | ATF | Standard Hydraulic Oil |
| Primary Use | Automatic transmissions, power steering | Hydraulic systems, plant machinery |
| Friction Modifiers | Yes | No |
| Detergents | High | Low/Medium |
| Viscosity | Typically lower | Available in ISO grades (32/46/68) |
| Colour | Red | Clear/amber |
| Manufacturer Compatibility | Very specific | Widely compatible across hydraulics |
These differences matter, especially in high-pressure hydraulic circuits.
Should You Replace Hydraulic Oil With ATF?
In commercial machinery and plant equipment: No.
In automotive hydraulic-assist systems: Possibly, if recommended.
At HTS Spares, we have had calls from operators who have mistakenly poured ATF into a hydraulic tank, usually because the fluid was ‘close enough’ or it was what they had on hand. Even a small amount of incompatible fluid can reduce lubrication quality, increase wear, and shorten the life of expensive components like hydraulic pumps, control valves, and rams.
How to Choose the Right Hydraulic Fluid
When selecting hydraulic oil, always consider:
- Manufacturer specification (most important!)
- Operating temperature
- Viscosity grade (ISO 32/46/68)
- System pressure
- Environment (indoor, outdoor, cold climate)
- Anti-wear needs
If you’re unsure, I would be happy to recommend the right hydraulic oil, plant lubricant, or OEM-approved alternative for your machine.
Conclusion: ATF Is Not a Universal Hydraulic Oil
To summarise:
- ATF is a specialised fluid, not a general-purpose hydraulic oil.
- It contains additives not suitable for most high-pressure hydraulic systems.
- Only use ATF where the manufacturer explicitly approves it.
- For plant, agricultural, and industrial equipment, stick with the correct ISO-grade hydraulic oil, such as those available in our Kompo® range.
Choosing the right lubricant protects your machinery, reduces downtime, and saves money, and that’s exactly what we aim to help you do at HTS Spares. For more guidance on this topic, please feel free to give me a call on 01432 373350 or email travis.knappett@htsspares.com.
