Tamaulipas → Coahuila · Autopista 40D Reynosa-Monterrey
On heavy-rain or dense-fog days the Reynosa, Tamaulipas, to Saltillo, Coahuila, leg routinely demands well more than the 3h 56m estimated: Autopista 40D Reynosa-Monterrey carries known hydroplaning hot spots and reduced-visibility corridors that justify dropping to 35 mph through a few short stretches. The outbound run covers 354 km (220 miles) over varied topography between Reynosa (the frontera con McAllen y polo maquilador del noreste fronterizo) and Saltillo (the capital coahuilense y centro de la industria automotriz Chrysler), demanding sharper attention on mountain descents and shoulder-less curves. Before pulling out, check brake-pad wear, tire tread depth, and washer-fluid level in the reservoir. Fuel spend holds near MXN 713.90 for the 29.5 liters (7.8 gallons) consumed. Even in adverse conditions, the flat tariff of MXN 6.50/km guarantees the standard outbound payout of MXN 2301.00 — log any incidental costs (extra toll, mandatory meal, emergency lodging) in a separate field on the Clara receipt. For the US professional driving the 354 km (220 mi) between Reynosa and Saltillo, reimbursement of MXN 2301.00 stays non-taxable to the employee when the employer follows an accountable plan under Treas. Reg. §1.62-2 and reimburses at or below the IRS standard mileage rate. US employers generally reimburse at the IRS standard mileage rate so the payment stays non-taxable to the employee under Pub. 463. Keep the IRS-compliant expense report (Form 1040 Schedule C, line 9) alongside the fuel receipt from any EIA-tracked retail station network pump used along the leg; Internal Revenue Service (IRS) examiners pull contemporaneous mileage logs first when auditing Schedule C unreimbursed business expenses, and the Reynosa→Saltillo corridor must show date, business purpose, and odometer readings.