"Viscosity- Resistance to liquid Flow" textbook definition from dictionary...
With that in mind, you want to satisfy the three major requirements of motor
oil, which are Lubrication, cooling and mechanical dampening.....
Use what the OEM manufactures recommend for viscosity, 10w40.
Fact it takes 2.5 times the mechanical energy to flow 20w-50 than 10w-30
oil synthetic or otherwise...i Recommend
AMSOIL Synthetic 10w-40 High Performance & SDF filters..
Feel free to e-mail me directly for more info...i have pics/Data....