Have never used it on any of my cars with automatic T. Put many a miles on them and never had a transmission go out on me. I had all the cars for at least 8 years and lived in the North East for the most part with high Mountains It is not a bad idea but the E brack can get stuck in cold weather this happened to me a few times with my stick vehicles, but what can you do there? Transmissions are built tough and wont be damaged by using PARK for Parking of course the E Brake will not be hurt by doing this and it keeps the e brake in shape and lubed for whenyou need it