If you want to know which oil to use, first of all check your owners handbook for the required API group and SAE limits, then look at the oil finder or oil guide page of the engine oil company.
This is the oil finder page for Mobil:https://mobiloil.com/en/product-selector
All major brand engine oil companies have such an oil selection page on their web sites and it's a real good idea to check that any recommendations from forum members agree with those from the oil companies.
Some oil finders only list the best oil, when other products from the same company would be also be suitable. The best oil finders, like the Liqui Moly one, list all of the oils:http://www.liqui-moly.com/liquimoly/web.nsf/id/pa_eng_oil_guide.html
If you are buying a new car with an extended warranty that allows you to do your own oil changes, make sure you read all the terms and conditions.