What we have here are two Sedans from Buick with some differences, such as the model year, modifications, market segment, starting price, horsepower, and fuel economy. First of all, there is a $3,915 difference in the base MSRP. The 2013 Buick Regal GS, an older vehicle by three model years, has a higher starting price than the 2016 Buick LaCrosse. Also, the 2016 LaCrosse has bigger and thirstier engine; the 2013 Regal GS gets 1.5 more mpg. Among similarities are the body structure, market segment, ground shadow size, height, and maximum occupancy.