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

Variations in international prices of refined products (gasoline and diesel) over the last few weeks have influenced prices in Central America, however El Salvador ranks first with the lowest prices in regular and special gasoline, and second with the lowest in diesel prices.

Average prices of gasoline and diesel in Central America:
El Salvador 2,45 2,74 2,93
Guatemala 2,33 2,79 2,98
Honduras 2,91 3,45 3,75
Nicaragua 2,93 3,38 3,56
Costa Rica 3,14 4,20 4,42
Panamá 2,21 2,58 2,78(data taken from Latinol.com)

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Fuel Prices - August 1, 2016

August 2016

Price of gallon of regular gasoline: Panama $2.61, Guatemala $2.58, El Salvador $2.65, Honduras $3.20, Nicaragua $3.28, and Costa Rica, $3.93.  

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

Variations in international prices of refined products (gasoline and diesel) over the last few weeks have influenced prices in Central America, allowing El Salvador to be located in second position in terms of the lowest prices of gasoline and diesel Central America.

Fuel Prices - April 11, 2016

April 2016

Price of gallon of regular gasoline: Panama $2.46, El Salvador $2.58, Guatemala $2.59, Costa Rica, $3.11, Honduras $3.16 y Nicaragua $3.27.

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

The Ministry of Economy announced that on April 11 that the reference prices for gasoline, in force from 12 to 25 April 2016, will experience an increase in their prices up + $0.11, while a gallon of diesel has decreased by up to - $0.02.

Fuel Prices as of November 23, 2015

November 2015

Price of a gallon of regular gasoline: Panama $ 2.41, El Salvador, $2.54, Guatemala $2.59, Nicaragua $3.23, Honduras, $3.20, Costa Rica, $3.76.

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

The Ministry of Economy announced on November 23 that the reference prices for gasoline, effective from November 24 to December 7, 2015, will experience reductions of up to - $0.05, note that this is the ninth consecutive redution in regular and special gasoline; while diesel also features new low prices.

Fuel Prices up to November 9, 2015

November 2015

Price of a gallon of regular gasoline: $2,39, El Salvador $2,57, Guatemala $2,67, Nicaragua $3,20, Honduras $3,22, Costa Rica $3,77.

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

This week the international prices of oil derivatives have rallied to the downside, this is due to a global surplus of crude oil inventories, coupled with the persistence of weak economic data presented by China, raising concerns about a slowdown in demand from one of the world's leading oil consumers; while record production in Russia has exacerbated global oversupply and declining international prices of derivatives. Rising interest rates and the rising dollar is a determining factor in the drop in prices.