Hi guys, I live in a hot climate (Middle East), the weather temperature between 29C to 45C (86F to 113F) and even sometimes reaches 47C (117F). Owner's manual says "use SAE 5W30 or 10W30 fully synthetic oil". Should I follow owner's manual? or Should I use 20W50? Many people use 20W50 because it's hot climate. You should use 20W50 because owner's manual recommend 5w30 for cars in Europe, American ...etc. They always say don't use a light viscosity here. Is there a big difference between 5w30 and 10w30??? What should I use 5w30 or 20w50???? I own HOLDEN VE V8 L98 6.0L and it has only 35,000 miles (56000 km).