Originally Posted by re-rx7
I know but dont know why
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They use 5w50 due to having 50% more antiwear additives. Highest levels of Zinc and Phosphorous. The weight of the oil is meaningless as you already mentioned it being almost the same at temp.
I will most likely swap to the recommended track car oil as well. All the 0w20 recommended oils have very low Zinc and Phosphorous levels to protect catalytic converters and other emission equipment.
for Example 0w20 mobil 1 has 650 PPM of Phosphorous and 750 PPM of Zinc.
15w50 Mobil 1 has 1200PPM for Phosphourous and 1300 PPM for Zinc.
5w50 is in between the 2.