I have no plans to travel to Mexico so I won't really need to worry about carrying extra fuel if unable to find ULSD, I was referring to those who will be traveling to Mexico before they have completed the switch to ULSD.
You'll be missing out on the people, sights, sounds and the joy of meeting up with fellow travelers. There's rarely any ice and snow south of the border. Travelers can certainly carry as much extra fuel as they feel they need too.
The first time I put Pemex diesel in my 2015 truck, I had these visions of limping and sputtering all the way back to the border. It didn't happen, the truck purred right along. I noticed one regeneration cycle on the way down, in Arizona, none returning home.
If I were to purchase a new diesel vehicle today, I would make sure it has the ability to force a manual DPF regeneration cycle. My understanding is that Ford added what they call an OCR, 'Operator Commanded Regeneration', switch on the dash. It was/is a $250 option. Should Active and Passive DPF regeneration fail, the switch gives the operator the ability to park up and force a regeneration cycle.
The Geritol crowd have been running later model diesel trucks and RVs down into Mainland Mexico.
http://www.mexicorvbuddies.com/diesel.php
There's no guarantee that if a station has ULSD the signage will say so. Your looking for a black station sign out front that says "UBA" or "bajo azufre ultra". The RV crowd rumor is that, unless ALL Pemex stations carry ULSD, the current signage won't change.
http://bajamary.com/media/Mexico-Diesel.php
If anyone have questions, fire off an email to Ted White, he's been collecting data on running later model diesels in Mexico on higher sulfur diesel. He answered all the questions i asked.
whitetmp@aol.com