http://www.lubrizol.com/EngineOilAdditives/ACEA/ConferencePapers/FuelEconomy.pdf As I've said before, Europe doesn't have CAFE, but CO2 limits by any other name are a fuel economy standard. Couple of interesting points that I got out of it. * trends in basestocks was interesting, reduction in GrIV in passenger cars (more GrIII obviously), reduction in GrI in HDMOs; * OCI optimisation from an environmental perspective; * the chart of manufacturer's versus weight versus CO2 (mileage) was interesting. Cut the following chart out as an excerpt, as it demonstrates something that I have tried to convey a number of times. While HTHS is clearly the main factor in frictional losses and fuel economy, for a given HTHS it's counter productive to chase high KV100 (or VI), as losses in the non high shear areas (oil lines, coolers, filters, squirters etc.) are higher than a KV100 which is closer to the high shear @100. It was seriously part of my driver in buying Edge 5W30 A3/B4 over the marginally more expensive 5W40 (both were on massive sale, so both were really same price). Edit : note that the reference oil in the economy table is 15W40.