Castrol RX Engine Oils
Discover Castrol RX – our range of engine oils for commercial vehicles, delivering excellent protection for a long and healthy engine life.
For long and healthy engine life
Over time, the demands of commercial driving expose engines to harmful combustion by-products. These can lead to deposit build-up, oil thickening, and increased engine wear – all of which can affect long-term performance and reliability.
Castrol RX is designed to meet these challenges. It helps maintain engine cleanliness and reduces wear, supporting a longer, healthier engine life. Whether your vehicles operate in harsh environments, over long duty cycles, or across a variety of applications, Castrol RX delivers dependable protection. Its proven formulation works across a wide range of diesel engines, including those requiring API CJ-4 and earlier specifications.
The Castrol RX range is a versatile, multi-purpose, heavy-duty engine oil designed to provide superior protection within diesel engines.
Formulated for protection
The Castrol RX range is formulated with powerful cleaning agents that help prevent harmful deposits from building up on engine surfaces, keeping vital components cleaner for longer. Anti-oxidants work to slow oil degradation and resist thickening, helping the oil stay stable under heat and pressure. Together, these features ensure reliable protection of pistons and moving metal parts, reducing wear and supporting consistent engine performance across demanding operating conditions. By maintaining cleanliness and viscosity, the Castrol RX range supports long and healthy engine life, especially in high-load or extended-use situations
For engines that demand more
For those facing even tougher conditions, Castrol RX Super takes engine protection a step further. With advanced DuraShield Technology, it actively prevents soot particles from forming abrasive clusters that can cause metalto-metal contact. This technology also creates a durable protective layer on critical engine surfaces, delivering up to 40% better wear protection* compared to standard formulations – ideal for heavy-duty engines operating under severe loads and high soot levels
The range
The complete Castrol RX range of engine oils
Castrol RX Super
An advanced, heavy duty diesel engine oil. with specially engineered DuraShieldTM Technology delivers 40% better wear protection*.
Castrol RX Diesel
Multi-purpose, heavy duty diesel engine oil for high-speed 4-stroke engines using varied fuel qualities, compatible with EGR systems
Castrol RX Mono
A diesel engine oil designed for use in heavy duty diesel engines, hydraulic systems and transmissions that specify the use of monograde diesel engine oil
Castrol RX products and viscosities
Castrol RX Super 15W-40 CJ-4/E9
Castrol RX Super 15W-40 CJ-4/E9 is an advanced heavy duty diesel engine oil. It is suitable for use in high speed 4-stroke diesel engines that use a broad range of fuel qualities. It is compatible with diesel engines fitted with EGR and the latest exhaust after treatment systems such as; DPF, DOC and/or SCR.
Recommended for use in all naturally aspirated and turbocharged diesel engines fitted in trucks, tractors, buses, LCV’s and off-highway equipment, agricultural and fixed plant machinery.
Features & benefits
New and advanced Castrol RX Super 15W-40 CJ-4/E9 with specially engineered DuraShield™ Boosters delivers 40% better wear protection*.
One of the main causes of damage in modern engines is abrasive wear. Castrol RX Super 15W-40 CJ-4/E9 with DuraShield™ Boosters is proven in industry testing to provide protection to your engine in two ways:
- Under severe engine operating conditions soot can agglomerate to form large particles which displace oil on moving metal surfaces and results in metal to metal contact. DuraShieldTM Boosters helps to prevent the agglomeration of soot as well as protecting surfaces from wear.
- Provides a protective layer on the moving metal surfaces which resists break down even under difficult conditions.
*average of wear parameters in industry tests vs industry standard limits
Industry specifications
- ACEA E9
- API CJ-4
- JASO DH-2
- CAT ECF-3
- Cummins CES 20081
- DDC Powerguard 93K218
- Mack EO-O Premium Plus
- MB-Approval 228.31
- RVI RLD-3Volvo VDS 4
- Suitable for use in agricultural applications where API CJ-4 or ACEA E9 is required.
Castrol RX Diesel 15W-40 CI-4 Plus/E7
Castrol RX Diesel 15W-40 CI-4 Plus/E7 is a multi-purpose, heavy duty diesel engine oil. It is suitable for use in high speed 4-stroke diesel engines that use a broad range of fuel qualities. It is also compatible with diesel engines fitted with exhaust gas recirculation (EGR) systems.
Recommended by Castrol for use in all naturally aspirated and turbocharged diesel engines fitted in trucks, tractors, buses, LCV’s and off-highway equipment, agricultural and fixed plant machinery without DPF/DPD exhaust after-treatment devices.
Features and benefits
During its working life, your engine faces challenges from combustion by-products that can form deposits, and thicken the oil.
Castrol RX Diesel 15W-40 CI-4 Plus/E7 combats these issues in two ways:
- Contains cleaning agents which displace particles that may otherwise build up on your engine surfaces reducing deposits.
- Contains anti-oxidants which disrupt the chemical reactions that can lead to oil thickening.
- Castrol RX Diesel 15W-40 CI-4 Plus/E7 provides effective piston deposit control and maintains its viscosity to encourage long and healthy engine life.
Industry specifications
- ACEA E7
- API CI-4 PLUS
- CAT ECF-2
- Cummins CES 20077, CES 20078
- DDC Powerguard 93K214
- Deutz DQC III-10
- Mack EO-N Premium Plus
- MB-Approval 228.3
- MTU Oil Category 2
- RVI RLD-2
- Volvo VDS 3
- Meets requirements of MAN M 3275
Castrol RX Diesel 15W-40 CI-4/E7
Castrol RX Diesel 15W-40 CI-4/E7 is a multi-purpose, heavy duty diesel engine oil. It is suitable for use in high speed 4-stroke diesel engines that use a broad range of fuel qualities. It is also compatible with diesel engines fitted with exhaust gas recirculation (EGR) systems.
Features and benefits:
- Contains cleaning agents which displace particles that may otherwise build up on your engine surfaces reducing deposits.
- Contains anti-oxidants which disrupt the chemical reactions that can lead to oil thickening.
- Provides effective piston deposit control and maintains its viscosity to encourage long and healthy engine life.
Industry specifications
- ACEA E7
- API CI-4/SL
- CAT ECF-2
- Cummins CES 20077, CES 20078
- DDC Powerguard 93K215
- Deutz DQC III-10
- Mack EO-M Plus,EO-N
- MB-Approval 228.3
- MTU Oil Category 2
- RVI RLD-2
- Volvo VDS 3
- Meets requirements of MAN M3275
Castrol RX Mono 30 CF
Castrol RX Mono 30 CF are diesel engine oils designed for use in heavy duty diesel engines, hydraulic systems and transmissions that specify the use of monograde diesel engine oil.
Suits fleet operators who favour monograde oils and a common oil is preferred for both engine and powershift transmission.
Industry specifications
- API CF
Castrol RX Mono 40 CF
Castrol RX Mono 40 CF are diesel engine oils designed for use in heavy duty diesel engines, hydraulic systems and transmissions that specify the use of monograde diesel engine oil.
Suits fleet operators who favour monograde oils and a common oil is preferred for both engine and powershift transmission.
Industry specifications
- API CF
Frequently asked questions
Can the oil I use really make a difference to the health of my engine?
Using a quality oil from an experienced manufacturer can help protect the hard working parts of your engine, reduce downtime and keep it running as it should for
as long as possible.
How does a regular oil change help protect my commercial vehicles engine?
Regular oil changes ensure that your engine is consistently protected from harmful contaminants, excess deposits, and sludge buildup. Fresh oil forms a protective
barrier that prevents rust, corrosion, and excessive wear on internal engine parts. This protection helps extend the lifespan of your engine and reduces the risk ot
costly repairs or breakdowns.
How do I select the right engine oil for my truck?
To select the right engine oil, refer to your truck s owner manual for the recommended oil type, viscosity, and specification. Choose oil that matches your engine
(diesel, petrol, etc) and consider factors like climate, driving conditions, and whether you need synthetic or conventional oil. Always look for quality certifications like
API or ACEA, and if you re not sure, use our Product Finder tool or consult a professional.
