I just checked the specification for Mexican marine/agricultural diesel in the documentation Pemex sent to me last week. The spec for marine/agricultural fuel is listed as 500 ppm. The information is contained in Table 7 of the document, dated August 29, 2016 (Lunes 29 de agosto de 2016), and issued by COMISION REGULADORA DE ENERGIA.
The first sentence in this 176 page document (translated) states:
"Agreement by which the Energy Regulatory Commission issued the Official Mexican Standard NOM-016-CRE-2016, quality specifications of the oil".