Below is the Pemex website where their most recent pricing posts can be found - they are not always up to date but since they can only raise by about 11 centavos per month by law at the most these prices won't be that far off. The most recent post was Aug 2015 at 14.123 for diesel. Looking back over the year it has not changed much from month to month.
Pemex-Refining
Gasoline and Diesel Price Structure
Applicable as of 2014
(pesos per liter)
ACTUAL-MONTHLY
http://ebdi.pemex.com/bdi/bdiController.do?action=cuadro&cvecua=IPET31_I
http://ebdi.pemex.com/bdi/bdiController.do?action=temas&language=en
Pemex-Refining
Crude oil process by refinery, applicable as of 1991
Petroleum Products Production, applicable as of 1993
Petroleum Products Production by Refineries, applicable as of 2000
Gasoline and Diesel Price Structure, applicable until 2013
>>>Gasoline and Diesel Price Structure, applicable as of 2014<<<
On the above page you will see the link marked says 2014 but it will take you to 2015 - not surprised.
Today's currency conversion rate
http://www.xe.com/currencyconverter/convert/?Amount=1&From=USD&To=MXN
1.00 USD = 16.6567 MXN
US Dollar ? Mexican Peso
1 USD = 16.6567 MXN 1 MXN = 0.0600359 USD
Looks like a Peso is now worth about 6 cents US.
Mid-market rates: 2015-10-21 23:13 UTC
If I have the formula correct that comes out to about $3.20 US per US Gallon for diesel. We recently paid $2.04 in the US.
1 Gal = 3.78 liters
14.123 X 3.78 divided by 16.6567 = $3.20
Pemex Magna Gasoline for Aug 2015 = 13.337
Pemex Premium Gasoline for Aug 2015 = 14.243