I use a Blend 10-30 in my V-10 (motorhome) and V-6 (Ford Ranger). I use 5-20 syn with Dexos 1 in my Chevy Cruze because of the turbo.
5-20 in my MH and pickup used to simply blow out the tailpipe....having to add oil between changes. (every 4000) Not so with 10-30. Using 5-20 or similar thinner oil is SUPPOSED to give you better gas mileage (strictly an academic exercise) that, on paper, gives the mgfr. the ability to meet the Feds fleet economy standard. IMO....complete bs.
And..btw, there is nothing wrong with using fossil. Again...IMO