From a statement issued by the Ministry of Economy of El Salvador:

The Ministry of Economy announced on May 25, new variations in the reference prices for fuels, which are valid from May 26 to June 8, 2015.

Upward variations in international prices of refined products have influenced prices in Central America; however, El Salvador is in second place with the lowest prices in petrol and diesel.

Countries Diesel Regular Special
El Salvador $ 2.96 $ 3.27 $ 3.58
Guatemala $ 2.80 $ 3.22 $ 3.41
Honduras $ 3.33 $ 3.77 $ 4.08
Nicaragua $ 3.38 $ 3.92 $ 4.15
Costa Rica $ 3.36 $ 4.04 $ 4.22
Panama $ 2.71 $ 3.09 $ 3.34 (data taken from Latinol.com).

More on this topic

Fuel Prices up to June 9

June 2015

Gallon of regular gasoline: Panama $3.17, Guatemala $3.22, El Salvador $3.27, Honduras $3.33, Nicaragua $3.38 and Costa Rica $4.04.

From a statement issued by the Ministry of Economy of El Salvador:

The Ministry of Economy announced this June 8, new variations in reference prices for fuel, which will be in force from 9 to June 22, 2015.

Fuel Prices up to 12 May

May 2015

Price of a gallon of regular gasoline: Panamá $3,05, Guatemala $3,16, El Salvador $3,18, Honduras $3,67, Nicaragua $3,92 y Costa Rica $4,04.

From a statement issued by the Ministry of Economy of El Salvador:

Variations in international prices have been influenced by a growth in demand, higher than expected, and a slowdown in the supply of crude oil and its derivatives in the United States; in addition prices have been impacted by geopolitical problems in the Middle East.

Fuel Prices up to April 28

April 2015

Price of a gallon of regular gasoline: Panamá $2,09, Guatemala $3,02, El Salvador $3,04, Honduras $3,59, Nicaragua $3,74 y Costa Rica $4,04.

From a statement issued by the Ministery of Economy of El Salvador:

In recent weeks the international prices of petroleum products recorded the following variations:+4,42% in special gasoline, +3,33% for regular gasoline and +6,50% in diesel.

Fuel Prices up to September 16, 2014

September 2014

Prices of a gallon of regular gas: $3.90 Panama, $4.00 El Salvador, $4.01 Guatemala, $4.56 Honduras, $4.71 Nicaragua, $5.22 Costa Rica.

From a statement issued by the Ministry of Economy of El Salvador:

The Ministry of Finance announced this September 15th, the new changes in reference prices for fuel, which will be in force from 16 to September 29, 2014.