Full Synthetic does not scorch on hot internal engine parts, scorching makes carbon. Carbon makes abrasive and the black appearances.
Image is a northstar well over 100k miles and FULL SYNTHETIC oil changes of 10k miles each. The extended change intervals are more than reasonable engine protection and add to the savings of justifying the more expensive product.
I'll stick to my high zinc dino oil. I've been told that switching...especially with high mileage...is deadly to engine components.
I'd use the exact oil your owner's manual calls for, I don't care when that manual was written.
If you have your engine COMPLETELY rebuilt by a real engine/speed shop obviously using all new modern
materials, use what they tell you to use. Jimmy Reid told me to use Driven HR4 for ever and ever Amen
when they rebuilt The Ark's engine. https://drivenracingoil.com/i-30497805-hr4-10w-30-synthetic-hot-rod-oil.html