I. Introduction
For nearly forty years, NATO’s single fuel concept (SFC) has rested on one governing premise: that the performance cost of running land vehicles on F-34/JP-8 instead of diesel, the fuel they were designed to take, is fixed and knowable in advance. That predictability is what has made the performance cost acceptable – because the size and direction of the penalty is quantifiable, engines can be recalibrated once, for a known chemical gap, rather than requiring case-by-case testing every time a vehicle is fuelled.
This premise is now under pressure because of a development external to NATO’s own procurement or doctrinal processes: the European Union’s ReFuelEU Aviation. The regulation requires rising shares of sustainable aviation fuel (SAF) at EU airports, met, in significant part, through the same dual-use pipeline infrastructure NATO relies upon for its own forces, most notably the Central Europe Pipeline System (CEPS).
The regulation was not written with the military in mind, and existing literature has not caught up with what it does to fuel flowing through a network the two systems share. Because CEPS operates on a mass-balance accounting basis, a receiving military depot cannot necessarily determine which SAF pathway or what blend ratio is present in a given batch (Regulation (EU) 2023/2405, 2023, Recital 39, p. 10; Article 4(6), p. 16).
Ultimately, the engine-calibration approach that made SFC’s original substitution manageable depends on knowing the fuel’s chemical profile in advance. If a depot cannot know it, that approach cannot be applied, and the fixed reference point SFC’s doctrine has relied on for forty years no longer holds.
This paper proceeds in three stages. It establishes what made SFC’s original fuel-substitution penalty manageable. It shows how ReFuelEU Aviation and CEPS’s architecture undermine that precondition; and it argues NATO’s 2026 eastern-flank investment extends an unresolved problem rather than solving it.
II. The Single Fuel Concept
NATO’s single fuel concept (SFC) originated in response to a fundamental operational problem: deploying coalition forces on a shared battlefield with multiple incompatible fuel types. The underlying reasoning stemmed from the logistical advantage it provided in wartime, as a single fuel at shared operating bases eliminated the need to stock and route multiple distinct fuel types across coalition formations.
NATO’s transition toward a single kerosene-based fuel for land-based operations developed progressively during the Cold War. The first step came in 1986, when NATO agreed on F-34/JP-8 as the standard aviation turbine fuel for land-based aircraft, replacing F-40. This changeover “prompted studies and trials by nations into using F-34 in diesel engines as a replacement for F-54 diesel fuel” (NATO, 1997, Chapter 15, para. 1512).
Building on that, NATO formalised the decision to consolidate fuel use on the European battlefield in 1988 (Arkoudeas et al., 2003, pp. 1013-1025).
The doctrine also satisfied two further pragmatic goals: simplifying the supply chain for petroleum products and making more use of NATO’s extensive and expensive pipeline system during peacetime (Arkoudeas et al., 2003, p. 1013).
That pipeline system is the physical backbone of the doctrine, and it was dual-use from the outset. The Central Europe Pipeline System (CEPS), the largest of NATO’s pipeline networks, was conceived to serve a specifically military purpose: supplying the main allied bases. Still, its installations have carried both civilian and military traffic.
The network’s scale reflects the dual mandate: NATO describes CEPS as an approximately 5,300-kilometre system linking 29 NATO depots and six non-military depots, while also supplying major civilian airports (NATO, 2025a; Stoop et al., 2025, p. 8).
However, SFC’s logistical benefits are not free of cost at the engine level. Applying the regulation to land vehicles means diesel-engine vehicles are required to run on F-34/JP-8 instead of diesel fuel. However, diesel engines are designed and calibrated around the density and viscosity of diesel, whilst F-34/JP-8 is a kerosene with lower density and viscosity (Fernandes et al., 2007, p. 957).
A bench-test study conducted by the US Army and University of Michigan found that substituting diesel with F-34/JP-8 without recalibration produced a measurable performance penalty; the reported effects included an 11.7% reduction in fuel mass delivered and a 13.7% drop in torque (Fernandes et al., 2007, pp. 957, 962).
Because that penalty only appears when the substitution is made without adjustment, some engines can be adapted to the fuel switch through appropriate calibration and operating adjustments. Ultimately, F-34/JP-8 cannot be treated as a universally interchangeable, drop-in replacement for diesel without regard to engine design or manufacturer guidance (Fernandes et al., 2007, p. 962).
About the author
Caelinn Cavalli is a Defence & Security research trainee at Finabel.