Gains in fuel economy with modern technology, SAE 5W-20 engine oils (GF-3 quality) in two identical 1998 MY Buick Centuries equipped with the 3.1L engine were measured in the EPA FTP test. These oils resulted in 1.0-2.2% gains in combined fuel economy (average 1.5%) over a typical GF-2 quality SAE 5W-30 oil. No significant gains in FE were observed during the cold transient portion of the FTP test. Engine oil temperatures were also reduced by 1-2°C with the SAE 5W-20 oils compared to the SAE 5W-30 oil. Of the two test oils, the one formulated with a Mo-type friction modifier additive was about 0.5% more fuel-efficient than the one formulated with an organic-type FM additive. Of the two vehicles, the one with the inherently poorer FE performance showed higher gains (expressed as percent improvement in FE) with the SAE 5W-20 oils than the other vehicle. Potential carry-over FE effects were observed with the oil containing the organic-type FM additive, but these effects were not verified.