Between 1980 and 1992, the Pioneer 10, Voyager 2, and Pioneer Venus Orbiter (PVO) spacecraft were in locations that made them were well-suited to search for radial trends and longitudinal asymmetries in solar wind parameters. Pioneer 10 and Voyager 2 travelled between the heliocentric distances of 21–54 AU and 6–36 AU respectively. Pioneer 10 was headed downstream with respect to the local interstellar medium (LISM) while Voyager 2 was headed upstream. Meanwhile, PVO was at 0.72 AU. We use data from these three spacecraft and Pioneer 11 to search for and set upper limits on possible asymmetries in solar wind velocity and temperature and on possible deceleration of the solar wind as a result of its interaction with the LISM.