Shell makes i think 2 20W-50 HDEO's, Rimula R3-X and R2 Extra, both diesel only rated, no gasoline engine ratings, 20W-50 is rare among HDEOs.
I've seen all these viscosities of HDEO :
5W-30
10W-30
15W-30
SAE 30
SAE 40
SAE 50
5W-40
10W-40
15W-40
20W-40
20W-50