Short answer
E10 is gasoline with up to 10 percent ethanol and is the most common US gasoline. E15 contains up to 15 percent ethanol; EPA waivers issued in 2010 and 2011 allow it in model year 2001 and newer cars and light-duty trucks, but not in motorcycles, heavy-duty vehicles or nonroad engines such as boats, snowmobiles and lawn equipment. E85 is a separate flex-fuel product.
What the labels mean
ASTM D4814, the US specification for spark-ignition engine fuel, covers gasoline including blends with up to 10 percent ethanol, which is why E10 is effectively ordinary pump gas. Fuel with 51 to 83 percent ethanol for flexible-fuel vehicles is covered by a different specification, ASTM D5798, and is sold as E85 or flex fuel.
Who can use E15
EPA granted two partial waivers: one in October 2010 for model year 2007 and newer light-duty vehicles, and one in January 2011 extending that to model years 2001 through 2006. EPA did not approve E15 for motorcycles, heavy-duty vehicles or nonroad engines, including boat engines, snowmobiles and lawn and garden equipment, citing a lack of supporting test data.
Because E15 is sold alongside E10, EPA requires a warning label on E15 pumps. Seasonal fuel volatility rules have also affected when E15 is sold in some areas, and those rules have changed over time, so availability varies.
Ethanol in small engines and boats
Ethanol attracts water. In fuel that sits for weeks in a vented tank, such as a boat, chainsaw or generator, enough water can be absorbed that the ethanol and water separate from the gasoline and settle at the bottom of the tank. That layer can cause hard starting and corrosion and is not something an engine should draw in.
Equipment makers often recommend fresh fuel, a fuel stabilizer for storage, or ethanol-free gasoline where available. Check the owner’s manual for the maximum ethanol content it allows.
Checking your vehicle
The owner’s manual, and sometimes the fuel door label, states the maximum ethanol blend. A 2001 or newer car being legally allowed to use E15 does not mean every manufacturer recommends it; some manuals limit fuel to E10.
Frequently asked questions
Can I put E15 in my boat or lawn mower?
No. EPA’s E15 waivers exclude nonroad engines, including marine engines and lawn and garden equipment.
Is E85 the same as E15?
No. E85 is a flex-fuel product with 51 to 83 percent ethanol for vehicles designed for it. Using it in a non-flex-fuel vehicle is not appropriate.
Does ethanol-free gasoline have its own spec?
It is still gasoline under ASTM D4814; it simply contains no ethanol. Availability depends on the region.
General maintenance information. Always follow your vehicle or equipment manufacturer’s requirements and the current product data. Questions? Email [email protected].