Baby wipes and toilet tissue are essential to successful travel hygiene while traveling Mexico's highways where the Pemex gas stations are state owned. Unleaded gas, Magna Sin, is available through the country, as well as the new higher octane Premium gasoline. It is a well known fact, no doubt eventually to be documented by medical research, that Ruffles, Doritos, Cheezets, or any snack food with artificial flavoring, taste and ingredients, preferably fried in pig fat, is necessary to sustain travel by train, plane or automobile. An added bonus is that on trips of more than 100 miles, they contribute not an iota of cholesterol, or calories, to the system. Remembering everything about the various routes within Mexico is as treacherous as trying to remember old love affairs.
Details are often fuzzy and sometimes the remembrance is worse or better than the reality.
Mexico Highway 54 south of Saltillo is a two lane highway you will have to share with 18 wheelers, buses, local traffic and a fair amount of horses, cows and goats. The quality of Highway 54 south of Zacateces diminishes considerably. On the other hand the scenery is often spectacular. About three hours outside of Guadalajara you will hit a stretch of beautiful, but high, mountains. Do not drive these mountains in the dark.