Federal law often worries about big things, like how much you can earn before the IRS sees where you can build. And then there’s this: Some gas pumps have a sticker warning about the minimum amount of fuel you can fill, which is four gallons. It’s a federal law, too – although it applies to specific fuel dispensed from a specific type of pump.
That fuel is E10, a grade consisting of 90% gasoline and 10% ethanol. Although this applies to almost all vehicles on US roads, the law is not specific to the fuel type. Instead, it only starts when the same pump also dispenses E15, which is a high ethanol blend that sits at 15% ethanol and 85% gasoline, through the same pipe and nozzle. These pumps are called blender pumps. If you use a nozzle dedicated to just E10, the restrictions disappear.
This is actually to protect the consumers themselves, especially those with older cars that do not support E15 fuel. After someone fills up with E15, about a third of a liter of fuel actually stays inside the pipe. If you are next in line and want to fill up with E10, what places in your tank first are actually closer to 33% E15. Even this much E15 with limited ethanol can damage older vehicles. To reduce any chance of that happening, the EPA has set the limit at four gallons. This helps reduce any remaining E15 to safe levels.
How common is it, and what if your tank is too small?
When the law was first announced in 2012, it generated considerable backlash. Jim Sensenbrenner of Wisconsin Jim Sensenbrenner actually went on record calling it an unwelcome intrusion into the lives of drivers although, at the time, the actual footprint of this law at gas stations was small as very few dispensed E15 through blender pumps. Today, their numbers have grown exponentially, as more than 5,000 stations across the US do so. Of course, this is still a small fraction of the 150,000+ total stations in the States.
When the law first came, the American Motorcyclist Association raised the alarm about the apparent problem with small gas tanks on motorcycles and lawn mowers. The average fuel tank capacity is just one or two liters. As a result, in February 2013, the EPA signed a third moratorium proposed by the Renewable Fuels Association, which stated that stations that dispense E15 must also provide at least one nozzle that dispenses fuel with 10% ethanol or less. These pumps will be labeled “Passenger Vehicles Only,” and gas stations must post signs directing customers to them.
Another thing to note is that this only works on E15, except for gasoline with higher ethanol blends. That’s because E15 is actually the legal limit for standard cars. Anything higher than that can only be handled by variable fuel vehicles, which can run well even on the E85 blend. These high-end mixers also use dedicated pipes, thus eliminating any chance of contamination.