2018 4runner in my case. Still on its original battery so that's probably getting a little weak. -10F starts fine, its when we get those -15 or -20ish nights where you can really hear it struggling and you hope it starts. Sure I could upgrade the battery but a block heater is a lot cheaper when my battery is just fine in > -10 degree weather. Plus you get a warmer engine with the better lubrication that provides for the motor until it heats up.