FuelMarble L
Fuel Efficiency Device for Fleets, SUVs & Heavy Diesel
- For SUVs, HGVs, fleets & heavy diesel
- DPF protection — extends filter life
- Drop-in coolant reservoir installation
- No tools or mechanic required
- Zero maintenance — permanent device
- Diesel, HFO & petrol compatible
- Free UK shipping
DPF-safe by design
FuelMarble L operates entirely within the coolant circuit. It never contacts your fuel, exhaust gases, or diesel particulate filter. No iron-based compounds. No ash residue. No filter contamination risk. Safe for Euro VI and Euro V aftertreatment systems — DPF, SCR, AdBlue, and EGR.
Check your vehicle size before ordering
Heavier vehicles may require 2 or 3 units of FuelMarble L. Vehicles over 4 tons need ×2 units; over 13 tons need ×3 units. See the size guide below ↓
Before you purchase — please note
FuelMarble is an aftermarket device. While consumer law generally protects your warranty rights, FuelMarble Ltd cannot guarantee your specific vehicle manufacturer's warranty response. FuelMarble does not dissolve, release chemicals, or modify any engine component.
By completing your purchase you confirm you have read our Return & Refund Policy, including the vehicle warranty notice and limitation of liability.
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Fleet Enquiry / Volume PricingDoes FuelMarble L Reduce Fuel Costs for Commercial Fleets and Marine Vessels?
Yes. FuelMarble L is a passive mineral ceramic device installed in the coolant reservoir of commercial diesel engines. It reduces fuel consumption by 7–15% by lowering cylinder wall temperature by 8–12°C, increasing peak cylinder pressure from 60 to 75 bar, and enabling more complete combustion — with no engine modification, no chemicals, and no maintenance.
- Yamanashi Kotsu bus fleet (Japan, 2024): 22.14% fuel saving on city routes, 15.90% on highway coaches — operator-documented day-by-day fuel logs
- TRES FELICES bulk carrier (55,810 DWT): 7.33–8.31% fuel reduction on North America–Japan route — wind-corrected operational data, Tamai Steamship Co., 12 months
- Miyazaki Express ferry (12,000 GRT): 5.9% fuel reduction — Japan MLIT Maritime Bureau government trial, 2010
- 10-truck HGV fleet ROI: £8,400–£18,000 annual fuel saving at 7–15% efficiency range. Investment: £5,190 for 10 units. Payback: 12–26 days at current diesel prices.
Mechanism independently verified by Kurume Institute of Technology (SAE 2008). Protected by Japanese patents JP4402484, JP2000-191338, JP2005-256802. Cleared by the Japan Fair Trade Commission (JFTC).
Pricing, Compatible Trucks & Fleet ROI — By Region
Select your region to see pricing tiers, compatible vehicles, and a 10-truck fleet ROI example in your currency. Your region is detected automatically — or toggle manually.
Pricing
Compatible vehicles
- HGVs, articulated lorries, and all heavy commercial vehicles
- LCV fleets: Sprinter, Transit Custom, Daily, Movano
- Agricultural machinery and tractors
- Any diesel vehicle over 2 tonnes GVWR with a coolant reservoir
Fleet ROI example — 10 trucks
Estimates based on 7–15% efficiency improvement from government-certified test data. Actual results vary. Full fleet ROI breakdown →
Which size do I need?
FuelMarble size is determined by vehicle weight and engine demand. Use this guide to choose the right unit.
Rule of thumb: below 2 tons GVWR → FuelMarble S; 2–4 tons GVWR → 1× FuelMarble L. Heavier vehicles add a unit per band. Marine vessels are dosed separately (1 kg per 10 tonnes) — see the marine sizing guide. Convert any weight with the ton-to-lbs converter.
Not sure? Contact our team and we will advise the correct product for your specific engine or application.
Everything FuelMarble L Delivers
Eight core performance and protection benefits — all independently verified through government-certified testing.
Up to 15% Fuel Efficiency Gain
The same government-certified efficiency gain as FuelMarble S, sized for vehicles between 2–4 tonnes GVWR. Measurable savings from the first full tank of fuel.
See verified test results →DPF Protection
Cleaner, more complete combustion reduces soot production — extending diesel particulate filter service life, reducing regeneration cycles, and protecting against costly DPF failure.
DPF & emissions guide →CO Reduced by 93%
Independent test results confirm a 93% reduction in carbon monoxide output — a critical metric for fleet compliance with clean air zone regulations across UK cities.
See emissions data →NOx Reduced by 98%
Near-complete elimination of nitrogen oxide emissions. FuelMarble L delivers exceptional NOx performance for heavy diesel engines operating in regulated environments.
See emissions data →Drop-In Coolant Installation
FuelMarble L places directly into your vehicle's coolant reservoir. No tools, no mechanics, no modifications. Each unit installs in under 60 seconds per vehicle.
Zero Maintenance Required
Once installed, FuelMarble L works permanently with no refills, no servicing, and no follow-up. Suitable for fleet vehicles covering hundreds of thousands of miles.
Made in Japan
Engineered and manufactured in Japan using precision mineral technology. FuelMarble L uses a larger mineral array to match the demands of bigger coolant systems.
About the technology →Works on HFO & Diesel-Powered Vessels
FuelMarble L's coolant-based mechanism works with both diesel and heavy fuel oil marine engines — making it suitable for commercial vessels and offshore applications.
The Numbers for a 10-Truck Deployment
FuelMarble L is built for scale. Select your region to see what a typical fleet deployment looks like financially in your local units and currency.
Based on 80,000 miles/year, 8 MPG (UK gallons), £1.48/litre diesel, 3 units per 13-tonne+ truck. 10% is the conservative efficiency figure — maximum verified is 15%. Actual savings vary by vehicle and route.
Protect Your Most Expensive Filter
Diesel particulate filter replacement costs £1,000–£3,500 per vehicle. Multiply that across a fleet with multiple premature failures per year, and DPF maintenance becomes a significant unplanned budget item.
FuelMarble L's cleaner combustion profile directly reduces the rate of DPF loading — extending service intervals and reducing the risk of blockage-related failure. How FuelMarble reduces emissions →
DPF cost savings per vehicle
Average DPF replacement cost. Avoiding one DPF failure per vehicle per year covers the cost of FuelMarble L many times over.
FuelMarble L Product Details
Proven on Commercial Vehicles
FuelMarble L's performance has been independently verified in real-world fleet deployments across Japan and South America.
Yamanashi Kotsu
Yamanashi Kotsu, a regional public bus operator in Japan, ran a structured trial across their diesel fleet. Results confirmed measurable reductions in fuel consumption and harmful emissions — consistent with laboratory performance data from Kurume Institute of Technology. The trial demonstrated real-world applicability of FuelMarble technology in high-mileage, continuous-duty commercial vehicle environments.
Tres Felices Bulk Carrier
The Tres Felices bulk carrier trial demonstrated fuel efficiency improvements in a heavy fuel oil marine environment — one of the most demanding applications for any combustion optimisation technology. The vessel's large HFO engine and high continuous load make it a rigorous test case, and results were independently documented over multiple voyage legs.
Compatible Commercial Vehicles
FuelMarble L is designed for the full range of European commercial diesel vehicles. The following models are confirmed compatible — any vehicle using a water-based coolant system qualifies.
Not listed? Contact our team for compatibility confirmation on your specific vehicle model or engine type.
5-Step Fleet Deployment
From assessment to full rollout — a typical FuelMarble L fleet deployment takes under one working day and requires no specialist skills or downtime.
- 01
Assess Your Fleet by Weight Class
Categorise vehicles by GVWR before ordering: light commercial up to 2 t requires one unit; 4–13 t requires two; over 13 t requires three. Mixed Euro IV, V, and VI fleets can all be treated in the same session — FuelMarble L is compatible with every Euro standard and all modern aftertreatment systems.
- 02
Install in Under 60 Seconds Per Vehicle
Open the coolant reservoir cap, drop FuelMarble L into the reservoir, replace the cap. No tools, no PPE, no drain-and-refill. A single depot operative can work through a 20-vehicle fleet in under 30 minutes during a routine morning vehicle check — zero vehicles taken off-road.
- 03
Record Pre-Installation Fuel Data
Note each vehicle's current MPG or L/100 km from the last three fill cycles. This baseline is essential for calculating your verified savings and presenting a clear ROI to your finance team or board.
- 04
Monitor Fill-to-Fill Over 90 Days
Compare fuel consumption fill-to-fill over the 90 days following installation. Most fleets see measurable improvement within 2–4 fill cycles. For independent verification methodology, see our guide at verified-results-fuel-efficiency.
- 05
Transfer Units at Vehicle Turnover
When a lease vehicle is returned, remove FuelMarble L from the coolant reservoir in seconds — leaving no trace on the vehicle. Reinstall in the replacement vehicle immediately. Each unit has an indefinite service life, so your initial investment travels with your fleet permanently.
Frequently Asked Questions
Also available
FuelMarble S
For personal cars & vans — £239
Reduce Your Fleet's Fuel Bill Today
Order FuelMarble L today. Fleet enquiries welcome. Free UK shipping. Secure Shopify checkout.