Vietnam’s biggest fuel distributors said they would complete a shift to an ethanol-blended product by Friday as part of a government programme to promote a more eco-friendly fuel.

State-owned PetroVietnam Oil Corp (PV Oil), which sells oil and fuels, will replace RON 92 fuel at all of its fuel stations with E5, a mixture of 95 percent of RON 92 and 5 percent of ethanol, by Dec. 15, its parent firm PetroVietnam said on its website on Monday.

Top fuel importer and distributor Petrolimex said on its website last week that its 2,400 stations across the country would have shifted to the ethanol-blended fuel by the end of this week.

Vietnam has been pushing for the E5 mixture as ethanol can be produced from cassava, making it renewable. Several factories have been set up specifically to process cassava into ethanol.

But critics and drivers argue the mixture could cause fire or damage vehicles’ engines and parts. The government has said the mixture is safe, adding that drivers should use vehicles from a certain year of production, depending on the model, to ensure they are safe.

Another type of non-ethanol fuel, RON 95, is still on sale, but in smaller volumes.

Vietnam plans to complete the shift to the E5 mixer across all fuel stations by Jan. 1 next year.