When in sport mode, is it ok to let your car upshift for you instead of using your paddle shifter?

 

Of course!

 

Really? LoL I always thought it was bad to let the rpms run so high and that the auto shift was just a backup in case you forgot to shift...So it's not bad for the transmission?

 

Nope... it is an automatic transmission - the computer know perfectly well when to shift.

 

As said, everything nowadays is computer controlled. The only possible danger that I can think of that you might hurt the engine or transmission is by revving high when the engine or transmission is not sufficiently warmed. The computer might even prevent that - I'll let you experiment on your car. Even with a manual transmission, the ecu will stop the engine from over revving. With a manual, you can over rev by shifting into a too low gear, but an auto will disable downshifts to prevent that. Heck, we've seen in another thread that the computer will disable upshifts with the ac on to help cool the tranny.

Driving with high revs may increase the wear rate of some components and use more gas, but these components would wear anyway, albeit at a slower rate. Warm your car sufficiently, and drive with confidence that your car will prevent you from doing something "bad."