A steel NATO jerry can and a plastic gas can both hold gasoline. They fail in completely different ways. Plastic fails slowly and quietly: fuel vapor works through the wall, sunlight makes the polyethylene brittle, the body swells against its own spout threads, and a self-venting spout turns a two-minute pour into ten. Steel fails loudly and rarely: it dents, and if the coating is chipped and ignored it can rust. Which one you should own depends on how long the fuel sits, where the can lives, and how many times a year you actually pour from it.
This guide walks through each failure mode with the primary sources behind it, is honest about where plastic is the right call, and ends with a short decision rule. If you want the design history first, start with what a NATO jerry can is.
Steel vs plastic at a glance
| Property | Steel NATO jerry can | Typical plastic (HDPE) gas can |
|---|---|---|
| Wall | 0.9 mm cold-rolled steel, powder coated outside, phenolic lining inside | Molded high-density polyethylene, often with a barrier layer or surface treatment |
| Fuel vapor through the wall | None. Steel is not permeable to hydrocarbons | Yes. Federal rules cap it at 0.3 grams per gallon per day |
| Sunlight | Coating fades over years; structure unaffected | UV oxidizes the polymer; surface cracks after prolonged exposure |
| Contact with gasoline | No absorption or swelling | HDPE swells roughly 10% by volume and softens while wet |
| Venting while pouring | Internal breather pipe lets air in as fuel leaves | Most post-2009 cans self-vent through the spout; slow flow is the most common complaint |
| Closure | Bayonet cam-lever cap, gasket, locking pin | Threaded screw cap, often with a spring-loaded or push-to-pour spout |
| Impact | Dents, stays sealed; fully welded, recessed seams | Stress-whitens, then cracks at seams and hinge points |
| Corrosion | Possible where the coating is chipped and left bare | None |
| Weight empty (5 gal class) | 9.5 lb (4.3 kg) for the 20 L | A fraction of that |
| Price | Higher | Lower |
| Best fit | Fuel that sits, vehicles, remote property, anything mounted outdoors | Weekly mower fuel, short trips to the pump, garage-only storage |
Where plastic is fine
Plastic is not a bad product. It is a product optimized for a different job. If you fill a can on Saturday and it is empty by the following Saturday, most of the failure modes below never get time to develop. A plastic can is light, it does not dent when it falls off a tailgate, it never rusts, and it costs a fraction of a steel can. For a homeowner topping up a mower, a snow blower, or a pressure washer from a can that lives in a closed garage, plastic is a reasonable choice and we would tell you that to your face.
The calculus changes when fuel sits. Backup generator reserves, ranch and off-grid supply, fuel mounted on the outside of a truck or trailer, hunting camps, boats, and anything you are storing so you do not have to think about it for a season: those are the cases where plastic's slow failures show up, and where steel earns its price.
Failure mode 1: the fuel leaves through the wall
Gasoline molecules are small enough to migrate through polyethylene. This is called permeation, and it is a big enough problem that the federal government regulates it. Under 40 CFR 59.611, hydrocarbon emissions from portable fuel containers "may not exceed 0.3 grams per gallon per day" as measured by a procedure that captures "diurnal venting emissions and permeation emissions" (40 CFR 59.611). Plastic can makers meet that limit with barrier layers, surface treatments, and thicker walls. The standard exists because untreated HDPE does not meet it on its own.
Steel does not permeate. There is no wall thickness, barrier, or treatment involved; hydrocarbons simply do not pass through it. A steel can that loses fuel is leaking at a seam or a seal, which you can see and fix. A plastic can that loses fuel is often doing exactly what the material does, and the only clue is a garage that smells like gasoline and a can that is a little lighter than you left it.
This is also why a plastic can that has held gasoline for years smells like gasoline even when empty and clean. The fuel is in the plastic.
Failure mode 2: sunlight
Polyethylene and polypropylene are polyolefins, and polyolefins have a specific weakness to ultraviolet light. A 2024 review in the journal Polymers summarizes it plainly: for these plastics "photodegradation proceeds via oxidation, leading to the destruction of their properties," and while they do not yellow, "the surface becomes cracked after prolonged exposure" (Nzimande, Polymers, 2024). UV stabilizers slow this down; they do not stop it. A red plastic can that has faded to pink on the side that faces the sun has already lost some of the flexibility that kept it from cracking when it was new.
Sunlight does very little to a steel can. The powder coat will fade over years of direct exposure. Under it, the 0.9 mm steel body is unchanged. A NATO can mounted on the back of a vehicle, in a rack on a trailer, or on a shelf in an open barn is in exactly the environment that ages plastic fastest and does nothing structural to steel.
Failure mode 3: the can swells against its own parts
HDPE absorbs gasoline. Oak Ridge National Laboratory tested plastic materials in reference gasoline and in blends with 25% ethanol and 16% to 24% isobutanol, and found that "high density polyethylene (HDPE) swelled around 10% for each test fuel," with "a small, but consistent, level of softening" in every formulation (Kass et al., ORNL / SAE, 2014). The interesting detail is that the base gasoline, not the alcohol, drove most of the swelling; the effect was "essentially the same for all test fuels." The plastic recovered its volume once dried.
Ten percent is a lot when the part that swells is a threaded neck and the part that does not is the cap. A wet, softened, slightly enlarged neck is why plastic can spouts weep at the threads, why caps that once sealed start to feel loose, and why a can that has been full for months can look subtly bloated. Every wet-dry cycle moves the parts relative to each other.
Steel does not absorb fuel and does not change dimension in contact with it. The cap on a Wavian can is a bayonet cam-lever, not a screw thread: it clamps a gasket down against a machined lip, and a locking pin holds the lever closed. The seal is the same on day one and after a decade of fills.
Failure mode 4: the spout
If you have poured from a plastic gas can made after 2009 you already know this section. The EPA said it in writing in a July 2025 letter to manufacturers: "Since EPA's evaporative emissions standards for PFCs went into effect in 2009, we have heard concerns from consumers, retailers, and elected officials about the performance of newer gas cans. One of the most common complaints is about slow fuel flow." The agency's own explanation is mechanical: "Without a vent, PFCs must self-vent through the spout which we believe may explain consumer complaints related to slow dispensing" (EPA, Clarification on Vents in Portable Fuel Containers, 2025). The same letter clarifies that the rules never prohibited vents, only required that any vent close automatically; most manufacturers left them off anyway.
The NATO can solved venting in 1937. An internal breather pipe runs from the cap opening to the far side of the body, so as fuel leaves, air enters through the same opening without glugging or surging. The cap itself has no pouring mechanism to jam or spring to wear out; you fit a separate spout when you pour and remove it when you are done. Fewer moving parts on the can means fewer things that can fail on the can.
Failure mode 5: impact and seams
Plastic cans are blow-molded or rotationally molded, which leaves a parting line around the body and thin spots at the handle and spout bosses. Repeated flexing at those points produces stress-whitening, then hairline cracks, then a leak. A plastic can that has been bounced in a truck bed for a season will often show white stress lines at the handle root before anything visibly breaks.
A NATO jerry can is two pressed-steel halves welded together along a recessed seam, with the three handles formed into the top, not bolted or glued on. The seam is fully welded and sits below the body surface, so a drop lands on the body panel rather than the joint. This is the construction detail that most cheap steel look-alikes skip: fully welded, recessed seams, no crimped metal like cheap knockoff cans. A dented steel can is still a sealed steel can.
Where steel loses
Steel has three real drawbacks, and we would rather you hear them here than discover them.
Weight. The Wavian 20 L weighs 9.5 lb (4.3 kg) empty. Full of gasoline it is in the neighborhood of 41 to 42 lb. A plastic can of similar capacity weighs a fraction of that empty. If you are carrying fuel by hand more than a few steps, that matters.
Price. A steel NATO can costs several times what a plastic can costs. The math works out if the can outlasts several plastic replacements, or if the fuel inside is protecting something expensive, like a generator that has to start. It does not work out for a can you use twice a summer.
Dents and chips. Steel dents where plastic would flex back. A dent is cosmetic on a jerry can, but it is permanent. If a drop or a scrape takes the powder coat down to bare metal and you leave it bare, the exposed steel can rust. Inside the can, a phenolic lining separates fuel from steel. Outside, a chip is a touch-up job with any enamel paint; ignoring it is how rust starts.
The decision rule
Ask two questions.
How long does fuel sit in the can? Days or a couple of weeks: plastic is fine. Months, or "I fill it and forget it until I need it": steel, because permeation, swelling, and UV are all functions of time.
Where does the can live? Inside a closed garage: plastic is fine. On a vehicle, in a rack, on a trailer, in an outbuilding with windows, or anywhere the sun reaches: steel, because UV and heat cycling are what age plastic fastest.
If either answer points to steel, a 20 L NATO jerry can is the standard answer for vehicles and reserves, and the 10 L is the same construction in a size one person can carry full for a distance. Both are built in Latvia to the same 1937 pattern, and both are the cans we have visited the factory to see made.
Frequently asked questions
Is a metal gas can better than plastic?
For fuel that sits for months or lives outdoors, yes. Steel does not permeate, swell, or degrade in sunlight. For fuel you use within a couple of weeks from a can kept in a closed garage, plastic is lighter, cheaper, and adequate.
Why does my plastic gas can smell like gasoline when it is empty?
Because HDPE absorbs gasoline. The plastic itself is carrying fuel that has migrated into the wall, which is the same permeation that federal rules at 40 CFR 59.611 limit to 0.3 grams per gallon per day.
Why do new plastic gas cans pour so slowly?
Most cans made after 2009 have no separate vent and must pull air back in through the spout as fuel leaves. The EPA acknowledged this as the most common consumer complaint in a 2025 letter to manufacturers and clarified that automatic-closing vents were always allowed.
Do steel jerry cans rust?
The inside of a Wavian can is lined with a phenolic coating that keeps fuel off the steel. The outside is powder coated. Rust is only a risk where the exterior coating is chipped to bare metal and left untreated, which a touch of enamel paint prevents.
Is a plastic gas can safe to leave in the sun?
Polyethylene oxidizes under UV light and its surface cracks after prolonged exposure. Any plastic can kept in direct sun should be inspected regularly for fading, stress-whitening, and hairline cracks, especially around the handle and spout.
Is a NATO jerry can a screw-cap can?
No. A Wavian NATO jerry can uses a bayonet cam-lever cap with a gasket and a locking pin. There are no threads to swell, strip, or cross-thread. The Wavian 22 L water can is a different product and does use a screw-on cap.
