The reason Ford made the change in 2011 was because they changed the mileage interval in which they recommended oil changes. In 2010, the recommendation for normal service was 7500 miles or 6 months whichever occurred first. In 2011, the recommendation was to rely on the message center or every 12 months whichever occurred first. The longer interval required the 5w30 due to possible oil dilution during the longer interval.