How holistic fuel management supports cleaner and more efficient vessel operations

The maritime industry's decarbonisation conversation has moved decisively toward Well-to-Wake to account for carbon not just from combustion, but from extraction, refining, and transport of fuel through to exhaust. It is the right framework for regulatory reporting, for CII ratings, and for understanding a fuel's true lifecycle emissions footprint.

But there is a practical reality that this conversation often obscures: ship operators control performance primarily on board. The upstream emissions profile of a fuel is fixed the moment it is bunkered. What happens between the bunker manifold and the exhaust stack is where your vessel's efficiency is either realised or lost and where most of the controllable losses actually occur.

What is Tank-to-Wake 

Tank-to-Wake is a systematic approach covering the entire onboard fuel lifecycle from the moment fuel enters your storage tanks to the moment exhaust gases leave the stack. Three distinct stages define it:

• Pre-combustion: fuel stability, water separation, storage compatibility, and sludge prevention
• Combustion: ignition quality, atomisation, burn efficiency, and energy conversion
• Post-combustion: soot management, heat recovery system cleanliness, and exhaust gas boiler performance

Losses occur at every stage. And crucially, losses in the early stages compound into losses downstream. Fuel that degrades in storage produces sludge that never reaches the engine. Fuel that ignites poorly generates excess soot that then deposits on heat recovery surfaces, reducing the efficiency of every subsequent combustion cycle. The system is interconnected and it responds to being managed as one.

Stage one: Fuel that reaches the engine at full value

Modern marine fuels are more chemically complex than their predecessors. VLSFO blends are frequently produced from multiple refinery streams and behave differently in storage than the HSFO they replaced. Bio-blends, increasingly relevant as operators seek FuelEU Maritime compliance pathways, introduce additional stability challenges that ISO 8217 alone does not fully address. CIMAC has documented that FAME-containing fuels can absorb significantly more water than conventional diesel or HVO, raising the risk of microbial activity, filter blocking, and accelerated degradation.

The practical consequence is measurable: industry data consistently shows that 1–3% of bunkered fuel can be lost as sludge before it ever reaches the engine. On a vessel consuming 8,000 tonnes annually at $580 per tonne, that represents up to $139,000 in paid energy that never generates propulsion. It also represents a direct, uncontrolled contribution to your reported fuel consumption and therefore your CII rating.

Two products address this stage of the Tank-to-Wake chain.

FuelPower Conditioner is formulated to improve fuel stability and separation performance. In a Lloyd's Register Product Performance Assessment (PPA), FuelPower Conditioner demonstrated up to a 46% improvement in Hotspin performance. Better separation means less sludge, more usable fuel, and cleaner fuel system components.

DieselPower Bio Enhancer is a multifunctional treatment developed specifically for diesel fuels, biofuels, and bio-blends. It improves oxidation stability, protects against corrosion, controls foaming, prevents injector deposits, and maintains water separability. In independent accelerated ageing testing, B100 FAME treated with DieselPower Bio Enhancer retained significantly higher oxidation stability after 12 weeks than an untreated sample (8.5 hours versus 6.5 hours under the EN 14214 / ISO 8217:2024 standard). The treated fuel remained compliant with the 8-hour minimum requirement; the untreated sample did not.

Stage two: Energy conversion, not energy release

Once fuel reaches the combustion stage, performance depends on how completely and efficiently the fuel's chemical energy is converted into useful mechanical output. Poor ignition quality leads to longer ignition delay, incomplete combustion, higher soot formation, and ultimately higher specific fuel oil consumption (SFOC) for the same power output.

FuelPower Catalyst addresses combustion quality directly. Using an iron-based catalytic mechanism, it supports reduced ignition delay, cleaner combustion, and lower soot formation, effects that carry downstream into exhaust system cleanliness. In independent testing conducted to IP 541, FuelPower Catalyst delivered over 6% improvement in Estimated Cetane Number (ECN), a meaningful gain in ignition quality for fuels at the lower end of the VLSFO specification range. The laboratory result was subsequently validated in a jointly witnessed engine trial with China Classification Society (CCS) on a MAN B&W 6S35ME-B9 two-stroke low-speed marine diesel engine operating on B30 VLSFO.

When FuelPower Catalyst was used in combination with FuelPower Conditioner, the trial demonstrated an observed SFOC reduction of between 1.51% and 2.17%. On an annual consumption of 8,000 tonnes, a 1.5% SFOC improvement represents approximately 120 tonnes of fuel saved, fuel that was purchased but would otherwise have generated heat, soot, and emissions rather than propulsion.

Stage three: What happens after combustion still matters

Tank-to-Wake performance does not end at the piston. After combustion, exhaust gases carry soot, unburnt carbon particles, and combustion by-products through the turbocharger, exhaust gas boiler, economiser, and ducting before reaching the stack.

Soot and firescale deposits on heat recovery surfaces are not merely a housekeeping issue. They reduce heat transfer efficiency, increase differential pressure across the exhaust gas boiler, raise the frequency and cost of manual cleaning, and create conditions for soot fires. For vessels operating in slow-steaming mode, where lower exhaust temperatures allow soot to accumulate more rapidly, this risk is elevated.

FuelPower Soot Remover Liquid Plus is formulated for continuous dosing into the exhaust stream, keeping heat-transfer surfaces cleaner between manual cleaning intervals. In a documented trial on a RoRo vessel, continuous use of FuelPower Soot Remover Liquid Plus extended the exhaust gas boiler cleaning interval from two months to 16 months — an eight-fold reduction in cleaning frequency. The measurable outcomes included more stable exhaust gas boiler performance, reduced maintenance demand, and lower operational risk over the period.

Soot Remover Powder remains the appropriate choice for higher-temperature exhaust conditions and periodic intensive treatment, complementing the liquid formulation in a complete post-combustion management programme.

The compounding logic of managing the full chain

A fuel that arrives at the combustion stage with degraded stability burns less efficiently, generates more soot, deposits more rapidly on exhaust surfaces, and reduces the efficiency of every combustion cycle that follows. The system is not linear; it is multiplicative.

The inverse is also true. Operators who address pre-combustion stability, combustion quality, and post-combustion cleanliness as an integrated programme consistently report outcomes that exceed what any single intervention achieves. Reduced sludge loss. Lower SFOC. Fewer unplanned maintenance events. Extended cleaning intervals. And a measurable, documented improvement in fuel efficiency that flows through to CII calculations.

This is what a holistic fuel management approach delivers: not a marginal improvement in one metric, but a controlled, systematically optimised onboard fuel system in which every tonne bunkered has a credible chance of contributing fully to propulsion.

The Tank-to-Wake opportunity varies by vessel, trade route, fuel type, and current treatment programme. A container ship running VLSFO has different pre-combustion risks than a ferry operating on B30 blends. A vessel slow steaming on a long Pacific crossing faces different post-combustion challenges than one on high-load North Sea trades.

Unitor™’s fuel treatment specialists work with technical managers and superintendents to assess the specific losses in a vessel's current onboard fuel chain and identify where treatment delivers the clearest return. If you are managing fuel efficiency improvements for CII compliance, exploring bio-blend handling for FuelEU Maritime, or simply trying to understand where your fuel spend is going, reach out to our Expert to optimise your fuel management.