Many manufacturers have shifted to 5W-20 from 5W-30 oil in new production vehicles. The 5W-20 is a thinner oil (at operating temperatures) and thus raises concerns as to whether it protects and lubricates as well as the thicker, previously recommended oil weight.
Ford states that the company has shifted to 5W-20 due to a multitude of benefits derived from thinner oil, including better lubrication and reduced wear oil pump loads. In addition, Ford states that thinner oils reduce start-up wear, a major source of total engine wear.
In order for an oil of 5W-20 weight to be approved for use in Ford vehicles from 2006 forward, the oil must have a American Petroleum Institute (API) certification seal on the oil container.
While GM does list various 5W-20 oils in its approved oil list, GM does not specify 5W-20 oils in its cars, continuing to recommend 5W-30 oil. As a related note, many oil companies sell 5W-20 oils which are in full compliance with GM standards, which include API certification.
