How cold does it have to be before diesel gels?

We are filled to the top w/ #2 diesel here in Denver and have started it at about 20 degrees. Doesn't seem to be a problem.

Started my MH yesterday at -12 got on highway and started generator to use electric heater, drove 300 miles straight #2 fuel.No problems.Most of the time what is called gelling of fuel is moistureor some water in filter freezing.
True gelled fuel,you will not get it going by changing filter,takes sitting in warm area to warm fuel.

You should be fine at 30F with #2 regular diesel. For comparison it was -36F here in Montana last week and I didn't have any issues what so ever. I had a 1/4 tank of #2 and then filled up the rest with #1. I'll use the 50/50 winter mix for when the temps stay below 20-30F. Anything above that and I'll use #2.

Thinking of it you might not even be able to get #1 diesel fuel down in Texas. Best of luck to you.

Dallas is showing 30F at the moment, you don't have to worry about it.

Assuming your engine has glow plugs, turn the key on until they go off, turn the engine over for a second until they come back on, stop turning the engine over, wait until they go off a second time and then proceed to start the engine.

Bill