www.forestfundamentals.com Oil Inserts for Use with UCO Original Lanterns Bushcraft UK

Oil Inserts for Use with UCO Original Lanterns

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£26.95

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At Forest Fundamentals, we are longtime UCO lantern users. Over the years, we’ve made numerous DIY Oil Inserts from old aerosol cans. Eventually, we decided to create our own—introducing the Forest Fundamentals Oil Inserts!

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DESCRIPTION

At Forest Fundamentals, we are longtime UCO lantern users. Over the years, we’ve made numerous DIY Oil Inserts from old aerosol cans. Eventually, we decided to create our own—introducing the Forest Fundamentals Oil Inserts!

COST EFFECTIVENESS: Oil Inserts are far more cost-effective than candles. A 20-pack of candles costs approximately £44.99 ($56.52) and offers 180 hours of burn time. In contrast, a 4-litre bottle of paraffin lamp oil costs about £16 ($20.12) and provides approximately 560 hours of burn time. That’s approximately 22p ($0.28) saved per hour of burning—excluding the cost of the oil inserts!

ADJUSTING THE FLAME SIZE: Another benefit of using an Oil Insert over candles is the ability to adjust the flame size. Simply lengthen the wick to make the flame bigger. Oil also burns brighter than candles and withstands wind more effectively.

EASILY REPLACE THE WICKS OUTDOORS: No special tools are needed to replace the wicks. Each Oil Insert comes with detailed instructions and 60cm of spare cotton wick, offering approximately 800 hours of burn time.

LONG BURN TIMES: We have maximised the size of the oil chamber for longer burn times. A full lantern holds 25ml of fuel and provides around 3.5–4 hours of burn time. For multi-day use, a small 500ml bottle of lamp oil will provide around 70 hours of burn time—equivalent to 8 replacement candles!

SAFETY-FOCUSED DESIGN: The inserts are CNC machined from 6061 aluminium. Corrosion-resistant O-rings ensure the Oil Insert is fully watertight to prevent leaks, allowing fuel to be safely carried inside. All edges are deburred to remove sharpness.

STORAGE BAGS & LANYARD TOGGLES: The bag contains any residue left on the insert after refuelling. The high-vis orange bags and toggles ensure everything stays visible and easy to find. During use, the insert lids also easily attach to the lanterns with the elastic lanyard.

NOT AFFILIATED, JUST COMPATIBLE: This Forest Fundamentals product is designed for compatibility with UCO Original Lanterns but is not affiliated with, endorsed, or manufactured by UCO. It is independently developed and produced by Forest Fundamentals.

DESIGNED FOR FULL COMPATIBILITY: The height of the inserts allows the lantern to fully close with the Oil Inserts inside for easy transport. They work just like candles—only with oil!

PLEASE NOTE: Forest Fundamentals Oil Inserts are designed specifically for UCO Original Candle Lanterns. Compatibility with other UCO models or brands is not guaranteed. Please see our store for available wick refill pack purchase options.

REPLACEMENT WICKS: We also offer 250cm cotton wick refill packs—please see listing for details.

COMPONENTS INCLUDED

• 1x Forest Fundamentals Oil Insert
• 1x Paper & PDF Instructions
• 4x Replacement O-rings
• 1x 60cm (23.62") of cotton wick
• 1x Orange Ripstop Nylon Carrying Bag
• 1x High-Vis Elastic Orange Toggle
• 1x Stainless Steel Wick Trimming Scissors

WHY DID WE DECIDE TO DESIGN OUR OWN OIL INSERTS?

Over the years, we created various DIY Oil Inserts using everything from mini aerosol cans to metal tubing and old bolts.

The biggest challenge we encountered with DIY options was achieving a watertight seal and replacing the wicks easily.

Eventually, we set out to solve these design flaws and upgrade DIY Oil Inserts by designing something fully compatible with the lanterns. Meet the Forest Fundamentals Oil Inserts!

MAIN FEATURES

• Save approximately 22p ($0.28) per hour of burning (excluding oil insert cost).
• Adjust flame size easily by extending the wick.
• Brighter and more wind-resistant than candles.
• Wicks are easily replaceable outdoors, no tools needed.
• A full lantern (25ml fuel) burns for 3-4 hours.
• A 500ml bottle of lamp oil provides 70 hours of burn time (8 candles).
• O-rings ensure watertight inserts, preventing leaks and enabling safe fuel transport.
• Inserts fit inside the lantern, allowing it to fully close for transport.

TECHNICAL SPECS & MATERIALS

• CNC-machined 6061 aluminum
• Scratch-resistant matte black anodizing
• Corrosion-resistant O-rings
• Ripstop nylon drawstring bag
• High-visibility elastic toggle/lanyard

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The Reviews Savings Calculator Design Info The Design Story Demo Vid Manufacturing Info FAQs

Product Gallery

Oil Inserts for Use with UCO Original Lanterns

$278 $400

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SHIPPING

Complimentary ground shipping within 1 to 7 business days

In-store collection available within 1 to 7 business days

Next-day and Express delivery options also available

Purchases are delivered in an orange box tied with a Bolduc ribbon, with the exception of certain items

See the delivery FAQs for details on shipping methods, costs and delivery times

RETURNS AND EXCHANGES

Easy and complimentary, within 14 days

See conditions and procedure in our return FAQs

Check Out The Reviews

A Detailed Look at the Design of Our Inserts

Optimised for Use with the UCO Original Lanterns

Throughout the design process, lots of design features were added to ensure full compatibility with the lanterns.

We designed the oil insert to be as large as possible to hold more fuel, while still allowing the lantern to close fully with the insert inside, making it easy to transport both items together.

Although the spring isn't necessary for the oil inserts, they still fit inside with it—helping keep everything together and reducing the chance of misplacing the spring.

Trimming the wick lets you adjust the flame size. We made sure the wick extends far enough to do this even when the oil insert is inside the lantern.

Like the UCO lanterns, we wanted to ensure the Oil Inserts remained lightweight and portable. The inserts are CNC machined from aluminium and have thin walls to reduce weight without compromising strength.

Replacing the Wicks and Refilling the Inserts

When designing the inserts, we focused on keeping wick changes and refills quick and straightforward. Our goal was to make sure that these tasks could be done outdoors, hassle-free, and without needing any special tools.

We made replacing the wicks easier by adding a second screw for threading them. Early prototypes showed that feeding the wick straight into the lid was tricky—trying to grip and guide it from the backside (especially outdoors) just didn't work.

For refilling, the lid removes completely, leaving a large opening to pour fuel into. The large opening helps reduce the chance of any accidental spills.

During design, we aimed to make the oil chamber as large as possible to increase burn time. It holds 25ml of fuel, providing roughly four hours of use. (Note: flame size will affect this.)

Other Design Features of the Inserts

Every closure on the inserts uses corrosion-resistant O-rings. These are hidden when the insert is closed to keep the design clean, while still ensuring fuel stays sealed securely during transport.

We opted for matte black on the first batch of the inserts (more colours are planned for later). Each insert also comes with a bright orange reflective elastic toggle, so they're easy to spot if dropped. The toggle also lets you secure the lid to the lantern while in use, so it doesn't go missing.

Being able to adjust the flame size is a key advantage of the inserts. We chose high-density 100% cotton wicks for their slow burn rate—even with a large flame, they hold up well. At a typical flame height, the wick will burn through just 2–8mm over four hours.

Transporting the Inserts Inside the Lanterns

Throughout the design process, lots of design features were added to ensure full compatibility with the lanterns.

We designed the oil insert to be as large as possible to hold more fuel while still allowing the lantern to close fully with the insert inside, making it easy to transport both items together.

Although the spring isn't necessary for the oil inserts, they still fit inside with it—helping keep everything together and reducing the chance of misplacing the spring.

Lightweight and Portable

Trimming the wick lets you adjust the flame size. We made sure the wick extends far enough to do this even when the oil insert is inside the lantern.

Like the UCO lanterns, we wanted to ensure the Oil Inserts remained lightweight and portable. The inserts are CNC machined from aluminium and have thin walls to reduce weight without compromising strength.

Replacing the Wicks Outdoors

When designing the inserts, we focused on keeping wick changes and refills quick and straightforward. Our goal was to make sure these tasks could be done outdoors, hassle-free, and without needing any special tools.

We made replacing the wicks easier by adding a second screw for threading them. Early prototypes showed that feeding the wick straight into the lid was tricky—trying to grip and guide it from the backside (especially outdoors) just didn't work.

Easy Refuelling and Long Burn Times

For refilling, the lid removes completely, leaving a large opening to pour fuel into. The large opening helps reduce the chance of any accidental spills.

During design, we aimed to make the oil chamber as large as possible to increase burn time. It holds 25ml of fuel, providing roughly four hours of use. (Note: flame size will affect this.)

Transporting Fuel Inside the Inserts

Every closure on the inserts uses corrosion-resistant O-rings. These are hidden when the insert is closed to keep the design clean, while still ensuring fuel stays securely sealed during transport.

Scratch-Free Finishing & Slow Wick Burn Times

We opted for matte black on the first batch of the inserts (more colours are planned for later). Each insert also comes with a bright orange reflective elastic toggle, so they're easy to spot if dropped. The toggle also lets you secure the lid to the lantern while in use, so it doesn't go missing.

Being able to adjust the flame size is a key advantage of the inserts. We chose high-density 100% cotton wicks for their slow burn rate—even with a large flame, they hold up well. At a typical flame height, the wick will burn through just 2–8mm over four hours.

The Story Behind Our Oil Inserts

The Design Process: Why We Chose To Design Our Own Inserts

At Forest Fundamentals, we are long-time UCO lantern users. Over the years, with the help of a few YouTube videos, we experimented with making several different oil inserts from old aerosol cans and metal tubing.

Although these inserts worked well, one of the biggest challenges with the DIY versions was achieving a watertight seal and dealing with issues when replacing the wicks.

Eventually, we set out to solve these design flaws and upgrade DIY oil inserts by designing something fully compatible with the lanterns.

The CAD And 3D Printing Prototyping Phase

From the start, we knew the inserts had to fit inside the metal candle casing of the UCO Original Lanterns. This gave us a solid guide to fine-tune the perfect size.

However, the slight angle at the top of the candle holder made things a bit tricky. We 3D printed multiple prototypes, tweaking the angle each time until we achieved the perfect fit.

With the 3D printed samples, we were also working to perfect the size of the inserts. Testing showed that the lanterns needed to hold around 25 ml of fuel for at least four hours of burn time. The challenge was making the oil chamber large enough while still allowing the lantern lid to close fully with the insert inside.

In the end, we shortened the lid and cap height while ensuring there was still enough material to grip. We wanted to keep the design practical without making the components too small or difficult to use.

As a company with some experience in CNC machining, we thought this would be a fairly straightforward process. Half a year and countless prototypes later, they're finally on the shelves!

The CNC Machining Prototyping Phase

Once we had the overall size figured out, we focused on fine-tuning the individual components.

Originally, the wicks were threaded directly into the top of the lids. However, because they needed a tight fit to prevent leaks, the process was very fiddly.

In the end, we designed a separate screw for the wick to thread onto, which then screwed into the lid. This made changing the wicks much easier and more practical.

Along the way, we also increased the length of the screw to ensure it could be threaded from both sides of the lid.

Ensuring the oil inserts were completely watertight was a challenge. The industry-standard O-ring sizes never quite fit the design, so it took a lot of back-and-forth testing before we finally found the right sizes that worked.

The Wick Testing & Development Phase

Arguably, the most time-consuming part of the process was developing the wicks!

We had two key goals: ensuring a slow burn rate and maintaining a steady fuel flow for a consistent flame.

We worked with manufacturers to create countless samples, experimenting with different widths and blends of cotton, fibreglass, and nylon to find the perfect balance.

We tested each wick for total burn time, fuel flow, and light output until we eventually settled on a high-density cotton wick.

Each wick typically burned for around 3–5 hours. A lot of the testing involved letting them burn in front of the TV in the evening while we took notes on the results!

Why Did We Decide to Design Our Own Inserts?

At Forest Fundamentals, we are long-time UCO lantern users. Over the years, with the help of a few YouTube videos, we experimented with making several different oil inserts from old aerosol cans and metal tubing.

Although these inserts worked well, one of the biggest challenges with the DIY versions was achieving a watertight seal and dealing with issues when replacing the wicks.

Starting the Design Process

Eventually, we set out to solve these design flaws and upgrade DIY oil inserts by designing something fully compatible with the lanterns.

Perfecting the Shape of the Oil Inserts

From the start, we knew the inserts had to fit inside the metal candle casing of the UCO Original Lanterns. This gave us a solid guide to fine-tune the perfect size.

However, the slight angle at the top of the candle holder made things a bit tricky. We 3D printed multiple prototypes, tweaking the angle each time until we achieved the perfect fit.

Refining Insert Size & Fuel Capacity

With the 3D printed samples, we were also working to perfect the size of the inserts. Testing showed that the lanterns needed to hold around 25 ml of fuel for at least four hours of burn time. The challenge was making the oil chamber large enough while still allowing the lantern lid to close fully with the insert inside.

In the end, we shortened the lid and cap height while ensuring there was still enough material to grip. We wanted to keep the design practical without making the components too small or difficult to use.

As a company with some experience in CNC machining, we thought this would be a fairly straightforward process. Half a year and countless prototypes later, they're finally on the shelves!

Optimising the Design for Changing the Wicks

Once we had the overall size figured out, we focused on fine-tuning the individual components.

Originally, the wicks were threaded directly into the top of the lids. However, because they needed a tight fit to prevent leaks, the process was very fiddly.

In the end, we designed a separate screw for the wick to thread onto, which then screwed into the lid. This made changing the wicks much easier and more practical.

Along the way, we also increased the length of the screw to ensure it could be threaded from both sides of the lid.

Testing O-Rings for Waterproofing

Ensuring the oil inserts were completely watertight was a challenge. The industry-standard O-ring sizes never quite fit the design, so it took a lot of back-and-forth testing before we finally found the right sizes that worked.

Our Criteria for Developing the Perfect Wick

Arguably, the most time-consuming part of the process was developing the wicks!

We had two key goals: ensuring a slow burn rate and maintaining a steady fuel flow for a consistent flame.

Testing and Developing Different Wicks

We worked with manufacturers to create countless samples, experimenting with different widths and blends of cotton, fibreglass, and nylon to find the perfect balance.

We tested each wick for total burn time, fuel flow, and light output until we eventually settled on a high-density cotton wick.

Each wick typically burned for around 3–5 hours. A lot of the testing involved letting them burn in front of the TV in the evening while we took notes on the results!

View Savings Calculator

Cost Comparison: Candles vs Oil Insert Conversion Kit

Below, we've created a slightly nerdy but useful graph to show the total savings of using oil inserts compared to UCO candles. The insert line starts at £26.95 to account for the one-time cost of the insert itself. You can also enter the prices you pay for candles and paraffin to generate a more personalised comparison. This calculation is based on 25 ml of fuel providing 3.5 hours of burn time.

Select Currency

Price of a Single UCO Candle (£) Recommended: £2.99 Click to check candle prices (UK) Click to check candle prices (US)

Price of Paraffin Oil Per Litre (£) Recommended: £4.00 Click to check Paraffin prices (UK) Click to check Paraffin prices (US)

UCO Candles

FF Oil Inserts

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Break-even Point (hrs)

(Approx 8-9 candles)

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Saving After 500 hrs

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Cost Per Hour (UCO Candle)

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Cost Per Hour (FF Oil Insert)

WATCH: New FF Oil Inserts for the UCO Original Lanterns – No More Expensive Candles!

Watch on YouTube

Manufacturing and Quality Checks

How We Build It: Precision CNC-Machined Inserts

The inserts are CNC-machined from 6061 aluminium, chosen because it is lightweight, strong, and has excellent corrosion resistance.

High corrosion resistance was especially important due to the inserts being used outdoors and featuring multiple threaded components. Any rust or corrosion around the threads would make it difficult to screw the lid on properly.

After CNC machining, the parts are anodised with a REACH-compliant (environmental regulations) matte black coating. The coating is resistant to scratches.

To ensure there are no sharp edges—especially around the threads—all parts also undergo a deburring process, which smooths out any rough or sharp areas.

Before shipping, each insert undergoes a final inspection to ensure everything functions properly, with special attention given to the threads and any defects in the O-rings that could affect the seal.

Frequently Asked Questions

Can I close the UCO lantern lid with the oil insert inside?

Yes, the inserts are designed for full compatibility with UCO Original Lanterns (this model only). The lantern lid will close completely with the insert and spring inside.

How much fuel do the oil inserts consume?

The rate of fuel consumption depends largely on the flame size. With a standard flame (using 2mm or less of wick), 25ml of fuel provides approximately 4 hours of burn time. A larger flame will increase fuel consumption, reducing overall burn time.

Can I store fuel inside the oil insert for future use?

Yes, the inserts are designed to be completely watertight. After securing the lids, there may be slight leakage initially due to excess fuel being compressed out of the O-rings. Once wiped away, no further leakage will occur. To prevent leaks, ensure the caps are tightly secured.

What types of fuel are compatible with the oil inserts?

The oil inserts are compatible with kerosene, scented lamp oils, and paraffin oil. However, we recommend using only lamp oil or paraffin oil, as they are less flammable than kerosene and provide a more stable flame. We have included a link in the instructions to the most affordable paraffin we could find on Amazon.

What is the total burn time of the oil insert on a full tank?

The total burn time depends on the flame size. With a standard flame (using 2mm or less of wick), 25ml of fuel (a full insert) provides up to 4 hours of burn time. A larger flame will consume fuel more quickly, reducing total burn time.

How long do the wicks last before needing replacement?

With 2mm of wick exposed (to produce the standard flame size), you can expect around 4 hours of burn time. Since the wick burns slowly, replacements are rarely needed. However, if the wick becomes too short, it will not reach the bottom of the container, preventing the remaining fuel from being drawn up and used.

We recommend using a 10–15cm wick and replacing it every 5–10 uses.

Is the flame size adjustable?

Yes. One of the key advantages of oil inserts over standard candles is the ability to adjust the flame size. This can be done by pulling the wick through slightly to expose more wick, which increases the flame size.

The lanterns function well with a larger flame, although this may cause increased soot buildup, which can be easily wiped away after use. The soot does not damage the lanterns.

Will using the oil insert cause soot buildup on the lantern?

Yes, after prolonged use or when using a larger flame, soot will begin to accumulate—mainly on the metal top of the lantern and around the glass. While it can be a bit messy to clean, it does not damage the lantern and can be easily wiped off after use.

How does the light output compare to standard candles?

Using 2mm or less of wick to produce the standard flame size results in significantly brighter illumination compared to candles. Oil burns more efficiently, producing a stronger light while also being more resistant to wind.

Additionally, the adjustable wick allows for greater control over flame size and light output.

What should I do if my oil insert has a defect?

The oil inserts are covered by a 10-year warranty that guarantees protection against defects in workmanship and materials. If you encounter any issues with the inserts, feel free to reach out to us—we're happy to help.

Please note that the warranty does not cover damage resulting from misuse, neglect, or improper handling.

Are usage instructions included with the oil insert?

Yes, full instructions and how-to videos are included. We can also provide PDF instructions in different languages upon request.

Is this product made by UCO or officially endorsed by them?

No, this is not a UCO brand or affiliated product. It is designed by Forest Fundamentals to be fully compatible with UCO Original Lanterns, but it is not manufactured or endorsed by UCO.

This product is designed and manufactured solely by Forest Fundamentals.

Do the oil inserts help save money compared to candles?

Yes! The oil inserts are far more cost-effective than candles. A 20-pack of candles costs approximately £44.99 ($56.52) and offers 180 hours of burn time.

In contrast, a 4-litre bottle of paraffin or lamp oil costs about £16 ($20.12) and provides approximately 640 hours of burn time. That's a saving of around 22.5p ($0.28) per hour of burning—excluding the cost of the oil inserts themselves.

What are the delivery times for the inserts?

We ship all orders within 1–2 days.

Delivery times:
UK: 2–4 days
EU: 3–6 days
USA: 4–7 days

If delays occur, we'll notify you promptly. All international orders include door-to-door tracking.

Did we miss something?

If you have any questions, don't hesitate to email us at salessupport@forestfundamentals.com, or visit our Contact Us page.