ANSWER 8.

The first letter S of SF refers to the suitability for spark ignition/petrol engines and the second letter F of SF indicates the rating of the oil. The further up the alphabet the higher the rating.
The first letter C of CD refers to the suitability for compression /diesel engines and again the second letter D of CD indicates the rating of the oil.
20w-50 indicates the viscosity rating or weight of the oil. The 20w of 20w-50 is a rating of the oil when cold and the second part 50 of 20w-50 indicates the viscosity rating of the oil when hot.

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