The purpose for 5W20 being specified (In the US) is for CAFE standards. It's all about improving fuel economy to avoid fines. The effect on each car type is minimal but it adds up and every .1 mile per gallon is helpful.
Red Line 5W30 would be one of my recommendations for the street used vehicles even if they're driven hard and tracked occasionally. It's viscosity after a short period is far superior to any non synthetic 10W40 AND EVEN MOST 20W50s. It's amazing to see what numbers become over time with a harsh environment. The fuel dilution found quite often in rotaries is another reason to consider your starting viscosity wisely.
Paul.
|