I checked at WALMART last Friday & they had none, my local NAPA jobber had a pretty good stock the last time I lokked, I can run diluted DEF in my ECO, so not too worried, I'm more worried about the lube oil shortage.
I been running that in all My DSL 2013-17, You need to be cautious on some 2017s for some trucks are equip with quality sensor trigger to 22% Urea all 2018s have the QS, so 1 Gallon DS to every 2.5 Gallons DEF is about 24% problem free, Thats a big drop that both the DEF pump/Injector life will be extended.
Sam's Club, Home Depot, and truck stops have plenty of DEF in stock...only the fool (Economic Ninja) on YouTube is spouting about. The real shortage is in Australia and Korea where they shut down their urea plants a few years ago because it was cheaper to purchase it from the Chinese. Now, they are paying the price. We have numerous urea plants in the U.S. and no shortage of the feedstocks.
I was at Sam's Club on Saturday and the had a full pallet on the floor and two more full pallets in the steel above. Home Depot have over sixty cases in stock and my local truck stop told me they have NEVER had an issue getting DEF and don't foresee any reason they would in the future.