Diesel Heater Fuel Tank: Size, Material and Mounting
A diesel heater fuel tank is the separate fuel container that feeds your parking heater. Sizes run from 5L to 30L, so the heater never drains your vehicle's own tank. Vvkb stocks three plastic sizes — 8L, 10L and 12L — and builds stainless steel and aluminum tanks to order.
The tank looks like the simplest part of a diesel heater install. It is also the part buyers replace most often. The thin container in a cheap heater kit runs dry overnight and goes brittle in the sun.
- Sizing: liters you need ≈ hours of heat you want ÷ 4. A 10L tank runs a 5KW heater roughly 40–74 hours.
- Material: black three-layer PE or stainless steel. White and clear tanks let sunlight into the diesel — Vvkb stopped making them.
- In stock: 8L (2.1 gal), 10L (2.6 gal), 12L (3.2 gal) — true rated capacity, not an inflated label.
- Made to order: 5L, 15L, 20L, 30L; stainless steel; aluminum to your own drawing. OEM and ODM welcome.
- Fits: any 2KW–8KW diesel air heater — Webasto, Eberspächer, Autoterm, and the Chinese diesel heater kits sold under names like Vevor.
- The cap must vent. A sealed cap starves your pump or collapses the tank.
What buyers call this part
The same part goes by half a dozen names, and they all mean the container that feeds the heater. You will see it sold as a diesel heater fuel tank or a heater gas tank. Other listings call it an oil tank, a fuel barrel, or a spare, extra, extended or auxiliary tank.
Transportable and moveable heater fuel tanks mean the same thing again. It is a tank you can unbolt and carry to the pump, rather than an internal tank plumbed permanently into the vehicle.
What size diesel heater fuel tank do you need?
Take the hours of heat you want between refills and divide by four. That gives you the tank size in liters, with margin. A diesel air heater burns 0.136–0.252 L/hr depending on heat level, so 0.25 L/hr is the safe number to plan around.
Cold nights push the heater to its high setting, where consumption sits at the top of that range. An insulated van on a mild night sits at the bottom. Plan for the cold night, not the mild one.
| Tank | Runtime at 0.136–0.252 L/hr | Who it suits |
|---|---|---|
| 8L (2.1 gal) | 32–59 hours | A weekend in a van or truck cab. The smallest tank worth fitting. |
| 10L (2.6 gal) | 40–74 hours | Most popular size. Caravans, campers and RVs on a long trip. |
| 12L (3.2 gal) | 48–88 hours | Trucks, boats and daily winter use. Thicker walls. |
| 15L (4 gal) / 20L (5.3 gal) / 30L (7.9 gal) made to order | 60–220 hours | Hot water systems, 8KW heaters, remote sites, harvesters and other farm machinery, twin-heater builds. |
Two numbers change the answer. A 2KW heater on low sips about 0.04 L/hr, which stretches a 10L tank past a week. A 5KW heater feeding a hot water system runs far harder than any air heater.
If you think in gallons, the made-to-order 20L is the closest thing we build to a 5 gallon diesel heater tank. The three stock sizes land at 2.1, 2.6 and 3.2 gallons.
When you are undecided between two sizes, take the larger one. A small diesel tank means more trips outside in the cold, and the price gap between 8L and 12L is small compared with the inconvenience.
Black, white or stainless steel: the material decides how long your diesel lasts
Sunlight reaching the diesel is what ruins fuel in a small tank, and a translucent white tank lets it straight through. Light plus warmth plus a little condensation feeds microbial growth — the sludge that diesel owners call diesel bug. That sludge blocks your filter and kills the heater's fuel pump.
UV attacks the tank as well as the fuel. It embrittles the outer surface of the plastic, and thermal cycling and vibration then turn that brittle surface into cracks. Cracks start where stress concentrates: at the outlet fitting, at mold seams, and around mounting points.
UV protection for a plastic oil tank comes from the color of the wall, not from a coating that wears off. Black pigment stops the UV rays that a translucent wall lets straight through.
How the three materials compare
| Material | UV protection | Best for | Watch out for |
|---|---|---|---|
| Black three-layer PE (in stock) | Opaque wall blocks light. Only the narrow level window is translucent. | Almost every install. Cannot rust, will not sweat condensation into your fuel, and flexes instead of splitting in deep cold. | Still a plastic tank. Mount it out of constant direct sun where you can. |
| Stainless steel (made to order) | Complete — no light passes at all. | Permanent exterior installs, boats, and sites where the tank takes knocks. | Heavier, and bare metal seams are the usual failure point on cheap steel tanks. |
| Aluminum / aluminium (made to order, your drawing) | Complete. | Weight-critical builds and odd shapes that have to fit a specific cavity. | Built to order only, so allow lead time. |
| White / translucent plastic | None. UV passes through to the fuel. | Nothing we will supply. | Discontinued at Vvkb. |
Durable diesel polymer fuel tanks are not all the same polymer. The Vvkb plastic tank wall is built from three layers of PE, thick and UV-stabilized. That wall resists the aging that turns thin single-layer tanks chalky and brittle.
In stock now: 8L, 10L and 12L plastic diesel heater fuel tanks
Three plastic sizes ship from stock. All three carry a base-mounted fuel outlet, a vented cap, and a way to read the fuel level without a dipstick. The differences between them are worth knowing before you choose.
| 8L (2.1 gal) | 10L (2.6 gal) | 12L (3.2 gal) | |
|---|---|---|---|
| Body | Black three-layer PE | Black three-layer PE | Black three-layer PE, thicker wall |
| Fuel level gauge | Central translucent window with printed scale | Central translucent window | External sight tube |
| Filler | Top-mounted cap | 45° angled filler neck | 45° angled filler neck |
| Cap | Standard or keyed locking cap. Both versions are vented. | ||
| Outlet | Barbed outlet at the base — gravity keeps the line primed and the last of the fuel drains cleanly. | ||
| Mounting | 8 × φ6 mounting holes, 150 × 150 mm spacing | Recessed bolt bosses with metal eyelets | Recessed bolt bosses with metal eyelets |
| Dimensions | 14.5 × 13.3 × 3.4 in (368 × 337 × 86 mm) | On request | On request |
These tanks connect to the fuel line that came with your heater. You keep your existing fuel pump and dosing line; only the container changes. That makes a tank the cheapest worthwhile upgrade on a Chinese diesel heater kit.
Custom diesel fuel tanks: 5L to 30L, stainless steel and aluminum
Anything outside the three stock sizes is made to order, including every metal tank. Vvkb builds 5L, 15L, 20L and 30L capacities, cylindrical and rectangular stainless steel tanks, and aluminum tanks from a drawing you supply.
- Capacity: 5L, 15L, 20L and 30L, plus bulk fuel tank sizes for onsite generator and heater sets.
- Stainless steel: a welded cylinder or a rectangular box, with mounting feet and strap clamps.
- Aluminum to your drawing: send dimensions and outlet positions and we build to them.
- OEM and ODM: your branding, your cap, your outlet thread, your carton.
Made-to-order tanks need a lead time and a minimum run. Send your heater model, the space you have to fill, and the capacity you want, and you get a drawing and a price back.
Vvkb builds these tanks in the same factory as the heaters. That is why distributors and diesel tank suppliers across Europe, North America and Australia buy both from one source.
Where to mount a diesel heater fuel tank
Mount the tank at or slightly above your heater's fuel pump, within a few feet of the heater, and out of constant direct sun. Those three rules solve most of the problems people post about after the install.
Height relative to the pump
The pump can lift fuel, but a short line that rises gently primes fastest and holds prime best. Mounting many feet above or far below the pump makes it work harder and invites air leaks. A base-mounted outlet helps here, because gravity keeps the line full even when the pump idles.
Inside or outside the vehicle
| Location | Argument for | Argument against |
|---|---|---|
| Inside a locker or under a bed | Cabin warmth keeps diesel above its cloud point. No UV at all. Protected from stone chips. | The vent will smell of diesel unless you route it outside. Takes storage space. |
| Outside — A-frame or drawbar | No fumes inside. Easy to fill from a jerry can. | Full UV and weather exposure. Fuel gels faster in deep cold. |
| Outside — rear bumper or rear door | Out of the way, good for caravans. | Long fuel line — some caravan installs run 6 m (20 ft). Vibration and splash are worst here. |
| Underfloor locker | Shaded, low, close to most heater positions. | Hard to reach for refilling. Check the cap clears the floor. |
Fixing the tank down
Spread the load, and bolt through the tank's own mounting points rather than strapping it into a generic holder. The 8L tank has eight φ6 mounting holes on 150 mm centers for exactly this reason. Two brackets concentrate every road vibration into two points on a plastic molding. Stress concentration is where cracks start.
- Clip the line every 30 cm (12 in) so it cannot vibrate and chafe through.
- Keep bends gradual. Sharp 90° bends restrict flow and trap air.
- Route the line well away from the exhaust and any other heat source.
Why the cap has to vent — and why your van smells of diesel
The cap on a diesel heater fuel tank is vented on purpose, and blocking that vent breaks the system in one of two ways. Air has to enter the tank as the pump draws fuel out. Both the standard and the locking Vvkb cap are vented for this reason.
Seal the vent and the pump pulls against a vacuum until it starves mid-cycle. Seal it on a warm day and let the tank cool, and the plastic can collapse inwards. One owner had a professional installer leave a sticker over the breather hole and found the tank sucked flat.
The diesel smell almost nobody diagnoses correctly
If your living space smells of diesel while the heater is off, the source is usually the tank vent, not the exhaust. A stock cap vents through a small pinhole. Any enclosed space holding a vented diesel tank will eventually smell of diesel.
The fix is to move the vent, not to block it. Fit a barbed fitting to the top of the tank, run a hose up high, then down and out through the floor. The loop stops fuel slopping out and the outlet sits outside your living space.
A diesel smell in the hot air from your vents is a different problem and a more serious one. Check the ducting under the heater for splits, and check the exhaust outlet is not venting against bodywork near a floor vent. Fit a carbon monoxide alarm either way.
Separate tank or a standpipe in your vehicle's own tank?
Fit a standpipe into your vehicle's main tank if you can reach the sender. Fit a separate tank if you cannot, or if you want the install fully reversible. Both are valid. One thing is not.
| Standpipe in the main tank | Separate diesel heater fuel tank | |
|---|---|---|
| Refuelling | Never think about it | A manual job, every few days |
| Install effort | High — drop the tank, drill the sender | Low — bolt it down and connect one line |
| Risk of stranding you | None if the pickup is cut short, so the heater runs dry before the engine does | None — fully isolated from the vehicle |
| Reversible | No | Yes |
| Best for | Vans and trucks you are keeping, where the sender is reachable | Caravans, boats, trailers, generators, hire vehicles, and any tank you cannot get to |
If you go the standpipe route, leave about 3/4 inch (2 cm) between the pickup tip and the tank floor. Sediment and water then stay below your intake. A fuel tank standpipe with the right thread makes that job repeatable. Full step-by-step wiring and fuel routing is in the diesel heater installation guide.
When an external diesel heater fuel tank is the wrong answer
An external tank is not automatically the better choice, and there are four situations where we would talk you out of one.
- Your vehicle's sender is easy to reach. If you can lift the sender through a floor hatch, a standpipe gives you unlimited runtime and no refilling chore. Fit that instead.
- The only mounting spot is in full sun with no shade. Choose stainless steel, or accept that a plastic tank in permanent desert sun will age faster than one in a locker.
- You need it inside a sealed living space with no route for a vent hose. The cap has to breathe. Without a path outside, the smell will find you.
- You are heating in sustained deep cold with untreated summer fuel. A small external tank has no thermal mass and gels before your vehicle's main tank does. Use winter-grade diesel, mount the tank inside, or run from the main tank.
Diesel gelling inside the vehicle's own tank is a separate problem. That is what an in-tank diesel fuel heater is for. Those heaters are sized for a vehicle's main tank and do not fit these portable containers.
Frequently asked questions
How long will a diesel heater run on one tank of fuel?
Between 32 and 88 hours, depending on tank size and heat setting. At 0.136–0.252 L/hr, an 8L tank gives 32–59 hours, a 10L tank 40–74 hours, and a 12L tank 48–88 hours. A 2KW heater held on its lowest setting sips about 0.04 L/hr and stretches a 10L tank past a week. Plan around the high figure, because the cold nights that make you run the heater hardest are exactly when you least want to refill.
Does a diesel heater fuel tank need to be vented?
Yes, and it is not optional. Air must replace the fuel your pump draws out. Block the vent and the pump pulls against a vacuum until it starves. Block it on a warm day and the tank can collapse as it cools. Every Vvkb cap, standard or locking, is vented. If fumes in your living space are the problem, extend the vent with a hose to outside — do not seal it.
Why does my van smell of diesel when the heater is not running?
Almost always the tank cap vent, not the exhaust. The stock cap breathes through a pinhole, so any enclosed space holding the tank will smell over time. Fit a barbed fitting to the tank top, run a hose up and then down through the floor, and the smell leaves with it. If the smell is in the hot air from your outlets instead, check the ducting for splits. Also check that the exhaust is not re-entering through a floor vent.
Will a white or clear fuel tank really damage my diesel?
Yes, because light reaching the fuel is what starts the trouble. Sunlight through a translucent wall, combined with warmth and a little condensation, feeds microbial growth. The resulting sludge blocks the filter and can kill the heater's fuel pump inside a season. UV also embrittles the tank wall itself, and cracks then start at the outlet fitting and mounting points. Black plastic and stainless steel both block the light. Vvkb discontinued its white 5L and 15L tanks for this reason.
Does the tank actually hold its rated capacity?
Yes. A Vvkb tank sold as 10L holds 10L. This is worth checking on any tank you compare, because a common shortcut is to label an 8L molding as 10L. When the capacity is overstated, the runtime you planned never arrives and you are refilling a night earlier than you budgeted for.
Can I run off-road, red or dyed diesel in a diesel heater?
Technically it burns the same, but check your local law before you do it. Off-road diesel is chemically the same fuel with a dye added; heaters do not care about the dye. What varies is whether your jurisdiction permits dyed fuel in that application, and dye can stain a translucent level window. Kerosene and winter-blend diesel are also commonly used. Never put petrol or a petrol blend in a diesel heater tank.
How do I add a bigger fuel tank to a diesel heater?
Swap the container and keep everything else. The tank connects to the same fuel line and the same pump you already have. A larger tank is a direct replacement: disconnect the line, unbolt the old tank, bolt the new one down, reconnect. Keep the tank at or slightly above the pump and within a few feet of the heater. Nothing about the heater, the dosing pump or the controller changes.
Where should I mount the tank — above or below the heater?
At or slightly above the fuel pump. The pump lifts fuel, but a short line that rises gently primes fastest and keeps prime longest. Far above or far below makes the pump work harder and lets air leaks show themselves. The base-mounted outlet means gravity keeps the line primed between cycles. The last of the fuel drains out instead of sitting in the bottom.
Can I mount the tank inside the van, or does it have to go outside?
Inside works and has a real cold-weather advantage, provided you vent the cap outside. Cabin warmth keeps the diesel above its cloud point, and there is no UV at all. The trade is the vent hose you must route through the floor. Outside mounting removes the fume question. It also exposes the tank to sun, weather and the deepest cold. A rear-mounted caravan tank can mean a 6 m (20 ft) fuel line.
My tank is leaking around the outlet fitting. Can it be repaired?
The outlet bung is the most common leak point on any plastic tank, and it is repairable — but check the cap vent first. Fuel weeping from a full tank while driving or parked on a slope is usually vent overflow, not a crack. If the outlet itself is weeping, plastic welding with matching PE filler rod is the only reliable repair. Epoxies and adhesives do not bond to polyethylene. A tank that is already UV-embrittled is not worth repairing.
Should I use a separate tank or fit a standpipe in my vehicle's tank?
Standpipe if you can reach the sender, separate tank if you cannot. A standpipe means you never refill anything, and cutting the pickup a few inches short guarantees the heater runs dry before you are stranded. A separate tank means no drilling, no tank drop, and a fully reversible install — the right answer for caravans, boats, trailers and generators. Do not tee into the engine's fuel line in either case.
Can I use a jerry can as a diesel heater fuel tank?
Yes, with a conversion kit, and it is the most common DIY diesel heater fuel tank. A kit adds a bulkhead outlet near the base of the can and a vented cap, and a metal jerry can blocks UV completely. Two cautions. Fit the outlet low and use a proper bulkhead fitting with a fuel-rated seal. A glued fitting on a thin wall is the first thing to weep. And check the can is diesel-rated rather than a water container, since some plastics soften on long contact with fuel.
Will diesel in a small external tank gel in cold weather?
Sooner than the fuel in your vehicle's main tank, because a small tank has almost no thermal mass. Diesel clouds around 32°F (0°C) and stops flowing somewhere between 14°F and -4°F (-10°C and -20°C) depending on the blend. Three things help: use winter-grade fuel, mount the tank inside where cabin heat reaches it, or run the heater from the vehicle's main tank. In-tank fuel heaters are built for a vehicle's main tank and will not fit a portable container this size.
Ready to upgrade your diesel heater fuel tank?
Vvkb has been building diesel heaters and their parts in China since 1996. The tanks come out of the same factory as the heaters. That means the outlet, the thread and the fuel line all match how a real heater feeds.
- Want a tank now, shipped to you? The 8L, 10L and 12L plastic tanks are in stock at our retail store.
- Need a custom size, stainless steel or aluminum to your drawing? Send the capacity, the space and your heater model.
- Buying for a fleet, or OEM and ODM? Ask for volume pricing and branding options.
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Replacing more than the tank? Browse all diesel heater parts and accessories, or the full range of Vvkb diesel heaters.
