Kinetic hydrate inhibitor formulations (KHIs) often contain thermoresponsive polymers which can precipitate and cause fouling problems if the temperature of the aqueous polymer solution is raised above the deposition point (Tdp). For example, this can happen at well head injection or during processing. Parts 1 (Kelland, M. A. Energy Fuels 2020, 34, 2643-2653, DOI: 10.1021/acs.energyfuels.9b04040 and 2 (Kelland, M. A.; Njau, J.-S. Energy Fuels 2020, 34, 4544-4553, DOI: 10.1021/acs.energyfuels.0c00497) in this series reviewed and evaluated nonpolymeric classes of additives that can raise the Tdp of such KHI polymers. Here we report experimental studies on raising Tdp by addition of a second polymer to two well-known KHI polymers, poly(N-vinylcaprolactam) (PVCap) and poly(N-isopropylmethacrylamide) (PNIPMAM). Both polymers have Tdp values of about 30-40 degrees C in deionized water at typical field dosages of 0.1-1.0 wt %. Promising additives that raised the Tdp value significantly at typical produced water pH values were tested for their effect on the hydrate inhibition performance of the KHI polymer. The increase of Tdp for some polymers was shown to be strongly dependent on concentration as well as pH. Some cationic polymers, such as polyvinylamine or polyethylenimine (linear or hyperbranched), had a good effect on raising Tdp, but the best results were obtained with sodium lignosulfonates, which gave at worst only a slight loss of KHI performance.