I use Magnatec diesel in the boat, and the car petrol version in my car, of the cold start-up protection. My car is 26 years old and still uses no oil between 10,000km services, and the boat similarly and it's 40 years old - appears to work for me. They are I semisynthetics...
Castrol Magnatec Engine Oil -10W-40, 5 Litre - Supercheap Auto Australia