Oil ( Oh there i've said it!)
Some useful basics:
Flash Point-temp at which a particular oil will burn
Pour Point-how cold can it get before the oil gets too thick to flow
Shear Point-What point does the oil break down
If you do some reading, you will see that synthetics vastly out-perform dino oils.
Had a Mazda 323 back in the 80's. Mobil 1 every 5000 miles.
@ 60,000 took the car in for a cam belt replacement as per the maintenance schedule
When I came back to get the car the service mgr asked me to "come out and look at something"
Promptly got the heebeegeebees
Service mgr took the cam cover off and asked if/when I had the head replaced as the inside looked like a new engine
I informed him that the engine had never been apart.
The only explanation was the oil