What is the base oil for Acura RSX?
The base oil for Acura RSX engines is 5W-30, and you can use either conventional mineral oil or synthetic 5W-30 that meets API SN or newer and ILSAC GF-5 or newer. This applies to both the base RSX with the K20A3 engine and the RSX Type-S with the K20A2 engine.
Oil grade and compatibility
Among RSX models from 2002–2006, Acura’s service guidance consistently points to a 5W-30 viscosity as the standard oil grade for engine protection and performance. The critical requirement is that the oil meets current API service classifications and ILSAC standards. While 5W-30 is the default, always verify the exact specification for your year and climate in the owner's manual or on the under-hood oil label.
Recommended oil types
These are common options that satisfy the RSX specification:
- 5W-30 synthetic oil (full synthetic or synthetic blend) meeting API SN or newer and ILSAC GF-5 or newer
- 5W-30 conventional mineral oil meeting API SN or newer
- 5W-30 high-mileage oils designed for engines with higher mileage (optional)
In short, choose a 5W-30 grade that carries the API SN or newer and ILSAC GF-5 or newer designation, and select synthetic or conventional based on your preferences and maintenance plan.
Choosing oil by climate and engine variant
Climate and engine condition can influence your oil choice and change intervals. While 5W-30 is standard, some drivers in very hot climates or with higher mileage may opt for synthetic formulations to maximize protection and extend drain intervals, provided the oil still meets the required API/ILSAC specifications. The RSX uses either the K20A3 (base RSX) or the K20A2 (RSX Type-S); both share the same general oil spec, but always confirm year-by-year in the manual.
Oil options by climate and mileage
Before selecting an oil, consider these common scenarios:
- Hot or high-load climates: 5W-30 synthetic oil is preferred for better high-temperature stability
- Lower-mileage engines in temperate climates: conventional 5W-30 is acceptable
- High-mileage engines (older RSX models): 5W-30 high-mileage formulations can help with sealing and viscosity retention
Regardless of choice, ensure the oil meets the specified API/ILSAC standards and follow the recommended maintenance intervals to protect the engine.
Maintenance and verification
How to verify you are using the right oil and maintaining your RSX properly:
- Consult the owner's manual or the under-hood oil label for the exact recommended viscosity and API/ILSAC specification
- Ensure the oil you buy is labeled with API SN (or newer) and ILSAC GF-5 (or newer)
- Follow the recommended oil-change interval for your oil type (conventional oil generally requires shorter intervals than synthetic)
Regularly check oil level and quality, and use the maintenance minder system if equipped to guide service timing. If you’re unsure about which oil to use for your climate or mileage, consult a dealership or a qualified technician.
Summary
For the Acura RSX, the base oil is 5W-30, usable in either conventional or synthetic form, as long as it meets API SN or newer and ILSAC GF-5 or newer. Always verify the exact specification for your model year and climate from the owner’s manual or dealer guidance, and follow the recommended change intervals to keep the engine protected.
