lots of choices depending on $$$. i like + use 10-30 fake synthetics as less VII to go from a 10W base oil to a 30W then at 100C operating temps but even thinner where the oil gets hotter. my loose 201 TT 225 Q 300 hp with its small 4.25 qt sump gets Redline 15-50 in the summer makeup oil but at change time its 1/2 red 15-40 + thats in Pa weather + rarely driven in winter. going to 15W oils increased my vacuum on my installed gauge + lowered my mild consumption! IMO those in hotter climated have NO need for thinner O W or even 5W oils!!