Can a Diesel Generator Run on HVO? What to Check

Many site managers now ask whether the diesel generator on their site can run on HVO. It is a sensible question. HVO is a paraffinic fuel that engine makers describe as a drop-in alternative to diesel, and it suits standby sets because of how well it stores. Yet the answer is not a blanket yes. Approvals depend on the manufacturer, the model and sometimes the duty.

This guide sets out what Cummins and Perkins publish about HVO, what changes in fuel use and storage, how warranty works, and the checks to make before filling a tank. It sits alongside our guides on whether diesel generators will be banned in the UK and the generator emissions compliance guide for UK sites.

What is HVO?

HVO stands for hydrotreated vegetable oil. It is made from waste cooking oils and plant oils through a process called hydrotreating, which removes oxygen and impurities and leaves a paraffinic hydrocarbon that is chemically similar to diesel. It is sometimes called renewable diesel. In Europe, the relevant fuel standard is EN 15940.

HVO is not the same as biodiesel. Biodiesel (FAME) is made by a different process, transesterification, and contains oxygen. That difference matters for stability and storage.

Perkins notes that FAME biodiesels can contain 10 to 12 per cent oxygen, which makes them less oxidatively stable, and that blends above 20% biodiesel can lead to bacterial growth that affects the fuel system. HVO does not have the same limitation and can be used neat or at any blend with diesel.

How HVO differs from diesel

Cummins lists the main differences from diesel as roughly 7% lower density, limited aromatic content, limited sulphur content, a higher cetane value and a slightly higher hydrogen-to-carbon ratio. Perkins' own tests found a density of about 0.785 g/cm³ for HVO against 0.8345 g/cm³ for EN 590 diesel, and a cetane index of around 84 to 90 against about 52.

Which engine makers approve HVO in generators?

The sets in our range use all three engine brands. The Cummins C55D5EQ and C66D5EQ use the 4BTAA3.3-G14 engine, the Pramac GBW22P uses a Perkins 404J-22G engine, and the Pramac P11000-1P uses a Yanmar engine. You can browse the Cummins, Perkins and Yanmar ranges for the full picture.

> Expert tip: A statement for a whole engine range is a starting point, not a guarantee for your unit. Ask the manufacturer or your supplier for written confirmation covering your exact model, its serial number and how you will use it.

A note on standby and prime

When Cummins announced its approval in 2021, it described it as covering standby applications. Its later FAQ is broader for generator sets, but still limits engines used in G-Drive applications to standby. Because the position can change, check the current Cummins fuels bulletin for your duty. Our guide to prime versus standby power explains the two ratings.

Does HVO affect the warranty?

It depends on the manufacturer and the product, so get this confirmed before you switch.

• Cummins says warranty is covered for the products listed for HVO use on its fuels bulletin, including the standby generator sets typically used in data centres. For a product that is not approved, Cummins says to contact your distributor.
• Yanmar's marine statement takes a different position. It says that after switching to EN 15940 HVO, any engine performance loss and higher fuel consumption are not covered by warranty. That statement is for its marine engines, but it shows that makers differ.

For the Cummins sets we supply, standby cover is two years or 500 hours and prime cover is one year with unlimited hours. Read the manufacturer's warranty statement and fuels bulletin, and ask us to check the exact model you are considering.

The fuel must meet EN 15940

The fuel specification is the single most important condition. Cummins requires HVO to comply with EN 15940 and says it can be sourced from any supplier whose fuel does. Perkins adds that HVO is highly refined and has lower lubricity than standard diesel, but that EN 15940 fuels are required to contain lubricity additives, so this is not a concern for compliant fuel.

Yanmar warns that renewable fuels that do not meet EN 15940 can cause fuel pump or injector seizure through poor lubricity.

In practice:

• Buy only fuel that is supplied as EN 15940 and ask for the delivery documentation.
• Treat "renewable diesel" labelling alone as insufficient.
• Keep the supplier's specification on file alongside your service records.

How HVO changes fuel use and performance

Both manufacturers expect a small increase in fuel use by volume, because HVO is less dense than diesel even though it carries more energy per kilogram.

• Cummins says HVO fuel will have up to 5% higher fuel consumption than documented on the data sheet and advises adding 5% to data sheet values. It also notes a potential mechanical power loss of 1 to 2%, but says that at most generator set power nodes there is enough margin that no derate is needed.
• Perkins' 1,000-hour test found HVO consumption averaged about 2 to 2.5% higher than EN 590 by volume, with a maximum of 3.7%. Load acceptance passed the ISO 8528 test, service intervals were unchanged and noise and vibration showed no meaningful difference.

To see what that means in practice, take the Cummins C55D5e. Its datasheet gives 12.0 litres an hour at full prime load, and our product page lists a 180-litre tank. These figures are illustrations, not guarantees:

So a tank of HVO lasts a little less long than a tank of diesel. If you have a tight autonomy requirement, size the tank with the larger allowance. For ways to run any generator efficiently, see our guide to fuel saving methods for generators.

Can you mix HVO with diesel?

Yes, according to both manufacturers. Cummins says any blend of diesel and HVO is acceptable, with no anticipated difference in engine behaviour apart from slightly greater fuel consumption. Perkins says its tests showed HVO works as a one-to-one replacement for diesel, both neat and blended, and that no tank cleaning or filter changes were needed when switching.

This flexibility is useful in practice. If HVO supply is interrupted, a site can top up with diesel. Perkins notes that availability of HVO can be limited in some regions.

Storage, contamination and cold weather

Storage. Perkins says HVO is resistant to oxidation and microbial growth and suitable for long-term storage without degradation. Cummins says its maintenance, storage and polishing recommendations are the same as for diesel, and that HVO from reputable suppliers tends to form less sediment than ultra-low sulphur diesel stored for long periods. It adds that the risk from water and dirt remains the same, and that if test data shows the fuel is clean, dry and sediment-free, polishing frequency could be reduced. Our guide to generator fuel contamination and site uptime covers the contamination risks that apply to any fuel.

Cold weather. Cummins advises confirming with the fuel supplier that the HVO will work at all site ambient conditions, and notes that traditional blending or anti-gelling agents may not be effective with HVO. This matters for outdoor standby sets in winter.

Additives and heaters. Cummins says many diesel additives can be used with HVO, but it endorses only two of its own, and that fuel heaters can be used with HVO.

Storage rules. The oil storage regulations apply to many kinds of oil, so check whether they apply to your tank. The GOV.UK guidance on oil storage explains when the rules apply to businesses.

Emissions and permits

At the tailpipe, the picture is similar to diesel. Cummins says NOx emissions are comparable and particulate emissions are lower with HVO. In Perkins' test, CO, CO2, NOx and soot were similar to diesel, with a noticeable reduction in hydrocarbons. Cummins says its EPA Tier 2 and TA Luft certifications are not affected and that its standard emissions data sheets are still used.

For permitting, Cummins notes that HVO may use slightly more fuel than diesel, so this has to be accounted for in permits that call for measuring fuel consumption. Smaller sets sit well below the thresholds for environmental permits, while larger sets can come close, so confirm where yours falls in the GOV.UK guidance on medium combustion plants and specified generators. Our generator compliance guide for UK site teams covers the wider obligations.

A checklist before you switch to HVO

1. Get written approval from the manufacturer for your exact model, serial number and duty (standby or prime).
2. Confirm the fuel is EN 15940 and keep the supplier's specification and delivery notes.
3. Check cold-weather suitability with your supplier for the lowest temperature at your site.
4. Recalculate autonomy using a 2.5 to 5% increase in litres per hour, and size the tank accordingly.
5. Keep to the same service schedule. Cummins and Perkins both say maintenance recommendations are the same as for diesel.
6. Test the generator on load after the first fill, so the change is recorded alongside your normal tests. Our guide to how often generators should be tested explains a sensible routine.

> Thinking of running a generator on HVO? Tell us the model you are considering and how you will use it, and we will check the manufacturer's approval for that set. Use the contact page or call +44 1302 700200.

Which of our generators could run on HVO?

The answer depends on the model and the manufacturer's current approval, so treat this table as a starting point for the question you should ask.

If you are choosing a generator for standby use, our standby generators range is a good starting point. For sizing, see our guide to what a 50 kVA generator can run, which uses the C55D5e figures above.

Frequently asked questions

Can I run my diesel generator on HVO?

Often, but it depends on the manufacturer's approval for your model. Cummins says it approves HVO in its generator sets with some exceptions, and Perkins says its 400 to 5000 Series can use up to 100% HVO. Always get written confirmation for your exact set.

Can I mix HVO and diesel in the same tank?

Yes. Cummins says any blend is acceptable, with slightly greater fuel consumption. Perkins found HVO works neat or blended without tank cleaning or filter changes.

Will HVO void my generator warranty?

Not necessarily. Cummins says warranty is covered for products listed for HVO use on its fuels bulletin. Other makers differ, and Yanmar's marine statement says performance loss and higher fuel consumption are not covered after switching, so check your manufacturer's terms.

Does HVO use more fuel than diesel?

Slightly, by volume. Cummins says to add up to 5% to datasheet figures, and Perkins measured an average of about 2 to 2.5%.

Does HVO store better than diesel?

According to Perkins and Cummins, yes. HVO resists oxidation and microbial growth, which makes it well suited to standby generators. Good fuel management still matters, because water and dirt contamination risks are the same.

Is HVO the same as biodiesel?

No. HVO is a non-oxygenated paraffinic fuel made by hydrotreating, while biodiesel is an oxygenated ester made by transesterification. Perkins notes that biodiesel blends above 20% can cause bacterial growth in the fuel system, which HVO does not.

Conclusion

A diesel generator can often run on HVO, and the engine makers' published guidance is encouraging. The conditions matter: EN 15940 fuel, written approval for your exact model and duty, a small allowance for higher fuel use, and a check on cold-weather performance. Treat the switch like any other change to a critical system: confirm it, record it and test it.

For more on where the sector is heading, read our guide on the future of diesel generators.

> Talk to a real person: Global Generators is an authorised Cummins reseller and an authorised Grupel and Pramac dealer, with new diesel generators in stock for UK delivery and export. Browse our diesel generators or the stock list, then contact our team on +44 1302 700200 or at enquiries@global-generators.com and we will help you check approvals for the set you need.