Does E10 Have a Shelf Life?

Feature

Written by Sabrina Deparine

Monday, 29 June 2009 10:06

Page views: 838

Country: Philippines

A couple of websites and articles have already published that ethanol-blended gasoline has shorter “life span” or shelf life than regular gasoline. Motorists have been advised to replace the gas in their fuel tank every 2 to 3 weeks because the shelf life of E10 gasoline is only around three months (90 to 100 days) given ideal environmental conditions.

Does E10 Have a Shelf Life?

Based on our research, there is no actual difference between the supposed “shelf life” of E10 and regular gasoline. According to the Fuel Ethanol FAQ website, both E10 or any ethanol-blended gasoline and regular gasoline can last for several years provided that the tank or container is sealed properly. Apparently, any type of gasoline is considered “expired” if it loses its octane, making the fuel inefficient. This only happens when the gasoline is exposed to air. For instance, when the container has some small openings where air can pass through. The air contains moisture which will condense in the gasoline. As such, the gasoline becomes diluted with water. The water will evaporate again but this time it takes with it some of the fuel additives and components in the gasoline. This takes away the octane.

E10 is perceived to have a shorter shelf life than regular gasoline because, as we have discussed in our article entitled “Is E10 Corrosive?”, the ethanol content in E10 is soluble in water which means that it can easily absorb more water than regular gasoline. A phase separation also occurs in E10 once it absorbs water. As such, more valuable components in the gasoline are lost once the water evaporates, making the E10 gasoline inefficient. In the words of Chevrolet’s Chief Engineer for Chevy Volt, Andrew Farrah, “the good stuff evaporates and the bad stuff condenses” because the good components evaporate with water while the contaminants from the water and air that the E10 had absorbed remains in the gasoline.

Car manufacturers are now trying to address this issue. For instance, Chevrolet cars are fully-equipped with completely sealed gas tanks to avoid water from creeping in and to prevent exposure to air. This is made possible by installing a semi-pressurized system. The gas tank size has likewise been reduced. The Chevrolet Volt, for example, only has a 12-gallon gas tank. This is done in order to reduce the unnecessary weight and to promote faster and quicker fuel turnover.

To date, car manufacturers are also looking into the plausibility of utilizing a sensor system. The said sensor will be installed in the car to detect contaminants present in the fuel. Once a contaminant is detected, the system will prompt the driver for action like recommending the replacement of gas in the tank.