It's starting to get a little colder here over the last few days. I think that it is going to be down around 5 or so tonight. I'll be using the block heater tonight for sure. I found that the truck will certainly start at these temperatures without the block heater, but it just seems to be a little easier on the truck and me (faster cab heat). Now today at work, it took a little longer for the grid heater to cycle... . but it fired right up. I would think that in most cases, as long as you wait for the "wait to start" light to go out, you should be ok.
Justin