No way you should try to drive 20 hours all at once. And I don t see why anyone would want to try since you can easily make the trip in two days. Are you not able to afford a hotel for one night or are you just in a hurry? Anyways, I ve driven this route before. It s a piece of cake. Once you ve departed PHX the only places you re going to encounter any traffic are Tucson and San Antonio. There s lots of open road, very little traffic, and the weather (for the first 3/4 of the trip) should be good. And a lot of the areas you ll be driving through (especially in Central Texas) are as pretty as heaven. I disagree with the second responder (Mountain). Since you re going to be more tired on the *second* day of driving (not the first) that means you should try to get as much driving done during the first day. So, I would try to make it to Fort Stockton, Texas. This was my first stayover point when I was driving from Phoenix to Florida last spring. Fort Stockton is about 650 miles from Phoenix, and I made it there in about 14 hours, but I drove 55-60 mph the whole way and made about 5 pit-stops. You can easily make it in 12 hours if you drive 60-65 and make fewer stops than I did. From Fort Stockton to Houston, you should be able to make it easily in 8 hours on the second day. Since Daylight Savings Time is not in effect, you only have to move your clock forward once. I drove in April and lost two hours just going from the AZ-NM border to just beyond El Paso. This sucked for me because it was already like 1 AM by the time I got to Fort Stockton.And also: I don t know what part of Phoenix you live in, but I lived in Goodyear (west valley) so it took me about 45 minutes just to get through the city (via the 202) and then pick up I-10. If you live somewhere closer then you can shave some of that off your total time. And if you can start out on a Saturday or Sunday morning (when traffic is lighter), even better.Happy Trails.
I ve made that trip in a single sitting... but it took closer to 26 hours because I had to take a lot of breaks as I was getting too tired to drive. Get a hotel in El Paso, its a good stopping point 8 hours from phoenix, and 12 hours from Houston. the second day of driving is a little longer than the first, but still doable. as far as the car, I havent a clue, you havent mentioned anything that would prevent it from making the trip.
You should NEVER attempt to drive 20 hours nonstop, that is very dangerous not only to yourself but to others on the road. Your car should be fine, take breaks get some sleep. You ll be fine.