HVO fuel, hydrotreated vegetable oil, is a renewable diesel that can be used in many diesel engines without modification, which makes it attractive to fleets that cannot yet electrify. The difficult questions are not about whether the engine runs, but about what emissions saving can honestly be reported, where the feedstock comes from and how the fuel is taxed.
This explainer covers the fuel standard, manufacturer approvals, the difference between tailpipe and lifecycle emissions, how the UK government’s 2026 greenhouse gas conversion factors treat HVO, what the Renewable Transport Fuel Obligation statistics show about feedstocks and how duty applies. It is written for fleet, sustainability and procurement teams, and it deliberately avoids quoting a single saving figure, because the honest answer depends on the supply chain.
What HVO fuel is and the EN 15940 standard
HVO is made by treating vegetable oils, used cooking oil or animal fats with hydrogen, which produces a paraffinic diesel rather than the fatty acid methyl ester (FAME) found in conventional biodiesel. The fuel specification is BS EN 15940:2023, published by BSI on 31 October 2023, which covers paraffinic diesel fuel from synthesis or hydrotreatment.
Two points from the standard’s scope matter for fleets. First, it allows up to 7.0 percent FAME by volume, so a product sold to EN 15940 is not necessarily pure HVO. Second, it applies to engines and vehicles compatible with paraffinic fuel, and BSI advises that vehicle manufacturers should be consulted about engine warranty before use. The standard defines two classes, high cetane and normal cetane.
Manufacturer approvals come before the fuel contract
Because EN 15940 is a different specification from the road diesel most engines are designed around, compatibility is a manufacturer decision, not a fuel supplier claim. Before switching, a fleet should check:
- whether the vehicle or engine handbook lists EN 15940 as an approved fuel for that model and model year;
- whether approval covers 100 percent HVO, blends, or both;
- whether any software, filter or service interval change is required;
- whether the warranty position is confirmed in writing by the manufacturer or dealer;
- whether plant and non-road machinery on the same site have separate approvals.
Approvals differ between manufacturers, models and engine generations, so a single list for the whole fleet is rarely safe. Keep the evidence with the vehicle record.
Tailpipe versus lifecycle emissions for HVO fuel
HVO fuel produces carbon dioxide at the exhaust, just as fossil diesel does. The case for it rests on the carbon in the fuel having been absorbed by plants during their growth, and on how the feedstock was produced. That makes the reporting boundary decisive. Our article on defining the reporting boundary before counting fleet emissions explains why.
The UK government’s 2026 greenhouse gas conversion factors, first published on 11 June 2026, handle this in three parts. In the full set spreadsheet:
| Factor (per litre) | Biodiesel HVO | Diesel, average biofuel blend |
|---|---|---|
| Scope 1 (direct combustion) | 0.03558 kg CO2e | 2.58354 kg CO2e |
| Well-to-tank (Scope 3 upstream) | 0.56439 kg CO2e | 0.61101 kg CO2e |
| Outside of scopes (biogenic CO2) | 2.43 kg CO2 | Separate line for the blend’s bio share |
The Scope 1 factor for HVO sets combustion CO2 to zero and counts only methane and nitrous oxide. The guidance says organisations must still report the combustion CO2 separately as “outside of scopes”, not in the total. The well-to-tank factor for HVO is close to that for forecourt diesel, which shows that most of the reported difference sits in Scope 1. The factors are averages, so a supplier’s own lifecycle data for a specific consignment may differ. Our guide to emission factor versions, units and intended uses explains how to record which set was applied.
Feedstock traceability and supply
The lifecycle saving depends on the feedstock. The Department for Transport’s RTFO statistics 2024 final report gives the most complete picture of what UK suppliers delivered under the obligation:
- HVO was 21 percent of verified renewable fuel in 2024, or 784 million litres equivalent, with volumes up over 50 percent on 2023.
- Used cooking oil was 46 percent of all verified renewable fuel.
- Used cooking oil from China supplied 31 percent of verified fuel, with over half of that used to produce HVO.
- Waste feedstocks made up 77 percent of verified renewable fuel.
- The average greenhouse gas saving for all renewable fuel was 80 percent against fossil fuel, or 77 percent including indirect land use change. The report gives no HVO-specific figure.
Under the government’s RTFO feedstock list, last updated on 15 September 2026, used cooking oil is a double-counting waste and Category 1 tallow a double-counting waste or residue. The 2026 RTFO compliance guidance requires evidence across every stage of the supply chain, independent verification and the retirement of sustainability documents once certificates are claimed. Fleets buying HVO should ask for the same kind of evidence, as our guide to defining an environmental claim and its evidence sets out.
Duty treatment and cost questions
HMRC’s hydrocarbon oil duty rates list heavy oil (diesel) and biodiesel at the same rate of £0.5295 per litre, effective from 23 March 2022. HMRC’s Excise Notice 179e defines biodiesel by an ester content of at least 96.5 percent by weight. HVO is not an ester fuel and the notice does not classify it by name, so fleets should confirm the duty basis with their supplier rather than assume a relief. Red diesel entitlement for specific uses is a separate question with its own rules.
On price, there is no official HVO price series comparable to the pump diesel series, and supplier quotes vary with feedstock, volume and delivery. A fair comparison sets out the price per litre against fossil diesel, any change in consumption, the cost of the evidence the fleet requires and the reporting value of the saving.
Key points for fleet and sustainability teams
- Check EN 15940 approval in writing for each model before switching.
- Under the 2026 DESNZ factors, HVO’s Scope 1 factor excludes biogenic CO2, which must be reported separately as outside of scopes.
- Well-to-tank emissions for HVO are similar to forecourt diesel, so report Scope 3 as well as Scope 1.
- Ask for feedstock type, country of origin, certification and RTFO status for each delivery.
- Confirm the duty basis with the supplier, and do not publish a single saving figure without consignment evidence.
This article is general information, not tax, legal or financial advice.
Sources
- BSI: BS EN 15940:2023 Automotive fuels, paraffinic diesel fuel from synthesis or hydrotreatment
- GOV.UK: Greenhouse gas reporting conversion factors 2026
- GOV.UK: Conversion factors 2026 full set (spreadsheet)
- GOV.UK: Renewable Transport Fuel Obligation statistics 2024 final report
- GOV.UK: RTFO and SAF Mandate list of feedstocks including wastes and residues
- GOV.UK: Renewable Transport Fuel Obligation compliance guidance 2026
- GOV.UK: Excise duty hydrocarbon oils rates
- GOV.UK: Biofuels and other fuel substitutes, Excise Notice 179e from 1 April 2022
Sources checked in November 2026. Rules, rates and schemes can change after publication, so check the linked official pages before acting.
