Portable Gas Cans and Fuel Storage: Filling, Storing at Home and Aboard, and Getting Rid of Old Gas

Look for cracks, soft or swollen plastic, rust on metal cans, a missing flame-mitigation screen, a cracked spout, or a cap gasket that's hard or missing. Squeeze the tank gently and sniff around the seams. Replace anything damaged; replacement spouts and caps should be made for that can. A leaking tank aboard a boat is a fire waiting to happen (see our fuel tank inspection guide).

Always set a gas can or portable tank on the ground to fill it. BoatUS explains that a can in a truck bed, on a plastic bed liner, in a trunk or on the boat deck can build up static electricity while fuel flows, and a spark can ignite the vapor. The BoatUS Foundation adds: fill on pavement or the dock so the can is grounded, and put an absorbent pad under it on the dock. Its boating course says portable tanks of 6 gallons or less should be taken off the boat to fill.

Before you start pumping, touch a metal part of the pump or your vehicle away from the nozzle to discharge static. Don't get back into the car during fueling.

Keep the metal nozzle touching the rim or opening of the can the whole time you fill. This gives static a path to the ground instead of jumping as a spark. Fill slowly and never lock the nozzle open on a can.

Don't fill a can or tank to the very top. BoatUS points out that gas from an underground storage tank is cool, and as it warms in a can sitting in the sun it can expand by as much as 10 percent. A full can then forces fuel out the cap, vent or spout. The BoatUS Foundation suggests filling tanks to about 90 percent; leave a similar air space in cans.

Treat fuel as soon as you buy it, not weeks later. Mercury says fuel can begin to oxidize and form gum in as little as two weeks, and Honda says that depending on your region's blend it can deteriorate in as little as 15 days, faster in heat and humidity. Add marine fuel stabilizer at the dose on the bottle (add it to the can before filling so it mixes as the gas flows in). Write the date and "stabilized" on the can.

In a vehicle, keep cans upright and strapped so they can't tip or slide, ideally in an open truck bed or on a trailer rather than inside the passenger area. If a can must ride inside, keep a window open and take it out as soon as you arrive. Never leave cans in a closed, hot car. Close any manual vent on a portable boat tank for transport.

Taking a small portable outboard home in the car too? Mercury's quick tip has you disconnect the fuel line (or close the fuel valve on a built-in-tank model) and let the engine run until it stops, with the gearcase submerged in the water or in a test tank or barrel, never dry; then fit the protective cap on the fuel connector so nothing drips in the vehicle. Let the water drain with the motor upright, and if you lay it down, put the side marked on the cowl decal facing up; Mercury warns that the wrong side lets oil run into the cylinders.

• Where: a detached shed or garage with ventilation, out of direct sun, and well away from anything with a flame or spark: water heaters, furnaces, dryers, freezers, workbenches with power tools. Never in the house, a basement or an attached space where fumes can reach living areas.
• How: caps tight, vents closed, cans upright on a hard floor and out of children's reach. The BoatUS Foundation recommends storing portable tanks out of direct sunlight in a cool, dry place to limit condensation.
• How much: keep only what you'll use soon. Many local fire codes limit how much gasoline you can store at home and in what containers; check with your local fire department.

• Secure portable tanks with straps or a bracket so they can't slide or tip while underway; the BoatUS Foundation's course says to do this after every fill.
• Keep tanks and spare cans in an open, ventilated part of the boat, never in a closed cabin, cuddy or storage locker that wasn't designed for fuel, and never near a stove, heater or battery.
• Keep them out of standing water in the bottom of the boat, and out of direct sun when you can.
• Open portable tank caps slowly (away from the engine) to release pressure before connecting the line.
• If you smell gasoline in the boat at any time, find out why before starting the engine.

Gasoline doesn't keep forever, and E10 gets worse with time:

• It oxidizes (Mercury: in as little as two weeks; Honda: as little as 15 days depending on blend).
• It evaporates: Practical Sailor cites BoatUS and EPA studies showing 5 to 20 percent of the fuel in a plastic can or tank can be lost in a year through evaporation and permeation, leaving fuel that is harder to start and lower in octane, even if it still looks fine.
• It absorbs water and can phase separate (see our ethanol fuel care guide).

Stabilizer slows this down. Mercury says its storage stabilizer keeps fuel usable for up to a year when fresh fuel is treated. As a practical rule, buy only what you'll use within a few weeks during the season, and plan to use or dispose of stored gas within the time your stabilizer label gives. Ethanol-free gas keeps better and is worth it for equipment that sits.

At the end of the season, run portable tanks down on the boat, or pour fresh, stabilized, non-premix gas into your car or other equipment that takes regular gasoline. Never put two-stroke premix into a car, a four-stroke engine or modern lawn equipment unless its manual allows it.

If fuel is stale (varnish smell, dark color), has water in it, or is premix you can't use:

• Keep it in a sealed, labeled approved container.
• Contact your local solid waste or environmental agency for a household hazardous waste (HHW) collection site or collection day. EPA lists gasoline-type products among HHW and warns never to pour them down a drain, on the ground, into a storm sewer or into the trash.
• Some auto parts stores or marinas accept used oil but not gasoline; call first.
• Never "burn it off," pour it into the boat's main tank to dilute it, or dump it in the water.

Wipe spills on land with an oil-only absorbent pad and let the pad dry outdoors away from ignition sources before bagging it for disposal per local rules. Don't hose gasoline into a storm drain. On the water, the BoatUS Foundation advises stopping the source, notifying your marina, containing the fuel with absorbent pads or booms and reporting it: by law, a spill that leaves a sheen must be reported to the US Coast Guard National Response Center (1-800-424-8802). It also suggests calling your insurer if the spill is substantial. Never use soap or detergent to disperse fuel on the water; it's illegal and pushes the fuel down into the water and sediment.

Gasoline inside the boat is a different emergency. BoatUS Magazine describes a boat refueled from a portable can that was found the next morning with gallons of gasoline in the bilge; while a mechanic mopped it up, something (possibly static or the bilge pump switching on) set off an explosion that burned two people and destroyed several boats. BoatUS's advice: for anything more than a few drips in the bilge, don't run pumps, blowers or switches and don't mop. Get everyone off, keep people away and call the fire department (911), which can blanket the fuel with foam before a salvor removes it.