Use a reg-lookup oil finder from a trusted brand site to match your car’s engine oil by registration number, then buy the exact viscosity/spec it recommends. If the lookup doesn’t return a result, check your owner’s manual or the oil cap, because the correct grade depends on your specific make, model, year, and engine.

Quick way to check

  • Enter your registration into an oil finder from Mobil, Castrol, Shell, Halfords, or a similar parts supplier.
  • Confirm the recommended viscosity, such as 5W-30, 0W-20, or 10W-40, before topping up or changing oil.
  • If there’s any mismatch or no clear result, use the vehicle handbook as the final check.

What the result means

Oil finders usually give you the viscosity grade and sometimes the oil type, such as synthetic, semi-synthetic, or conventional. Modern cars often use 5W-30 or 0W-20, but the correct choice still depends on the engine design and operating conditions.

Best next step

Send me your car’s registration plus the country it’s registered in, and I can help you work out what oil it should use.