When to apply fall lawn fertilizer in Dallas, DFW and north Texas is not the most important question to be asking. What type of fertilizer, weed control, and preemergent to apply in the fall in the north Texas area is the most important question.
First Question: When to put down and apply preemergent in north Texas to stop annual bluegrass?
Answer: You actually need to do it twice per year. Please go to this old blog post to get more details: https://turfgrassscience.com/uncategorized/when-is-the-best-time-apply-pre-emergent-in-dallas-north-texas/
Second Question: What is the best lawn fertilizer winterizer to use for grass in the fall?
General Answer: Best lawn winterizer is just a marketing term. "Winterizer" really just stands for something high in potassium. And most lawns need something high in potassium in the winter. K stands for Potassium. And it is the last number on the fertilizer bag. Example: 8-4-24. The 24 is the percentage of Potassium in the bag.
Better Answer: fall is the best time to do soil testing in Dallas. Then take the results of the soil test and apply whatever is deficient in your yard + some Potassium. In north Texas black clay there is a high chance you yard is going to be deficient in phosphorous (the middle digits) and along with having a high PH. And since it takes nearly 6-months to significantly lower ph in lawn soil, then doing it now just gets you ready for Spring. Read more about it here: How much sulphur to lower PH in lawn soil.
Phosphorous on the other hand can be absorbed into the soil pretty quickly. Please go to this blog post to read more about it: How to add phosphorous to the soil quickly.
Third question: When to fertilize lawn in fall in Dallas north Texas?
If you are not overseeding with perennial ryegrass or "winter rye" as Texans like to call it, then this will be based on the zone you live in. In north Texas we are in zone 7b to 8A (unless you are in the panhandle, which is not really considered north Texas). And since "winterizer" is not really a time sensitive application for lawns then applying the lawn fertilizer service anytime from October 1 to October 20th is going to be sufficient.
Lastly, if you have big bare spots from the near record heat this summer, or bare spots around trees fall is the absolute best time to trim trees and to do sod replacement. Please click this hyperlink to read about proper sod replacement: sod replacement services in Plano, Frisco, Dallas, Mckinney, Allen, Lewisville, Prosper, and other areas in north Texas.