It was 55 degrees this morning when I got to my car. I turned the key to the first notch and waited 1 minute before starting. It's hard to say if the injection heaters helped. Perhaps it did and it would have taken much longer to start without them. I expected it would turn over immediately, but instead it cranked 5 or 6 times before starting. I know the heater starts getting hot as soon as the key is turned to accessory, because I've felt it. I'm just not sure how long it takes to get really hot. I'll have to figure out some way to measure the heat and determine how long it takes the lines to get to a significant temp.