The short answer: diesel. The real answer is more nuanced — and getting it wrong can cost you thousands in repairs and lost efficiency.

Fuel is the lifeblood of your generator. It is also the single largest ongoing expense you will face — typically 85-90% of your total operating budget. Yet most generator owners give remarkably little thought to what goes into their tank.

I once consulted on a project where a client was spending $2,200/month more on fuel than they should have been — purely because they were using the wrong grade of diesel for their operating environment. That is $26,400 per year of unnecessary expense. For one generator.

This guide covers everything you need to know about fueling your Yuchai diesel generator: acceptable fuel types, quality standards, storage best practices, biodiesel compatibility, and the real-world impact of fuel choices on performance and longevity.

The Primary Fuel: Standard Diesel (Distillate Diesel)

Yuchai diesel generators are designed to run on standard distillate diesel fuel — the same fuel used in trucks, buses, and construction equipment worldwide. In technical terms, this is petroleum-based diesel that meets recognized international standards.

The two most important standards you will encounter:

• EN 590 (European standard): The most widely referenced diesel fuel standard globally. Specifies parameters including cetane number, sulfur content, density, viscosity, and cold filter plugging point. This is the gold standard for diesel generator fuel quality.
• ASTM D975 (American standard): The US equivalent, covering grades 1-D, 2-D, and 4-D diesel. Grade 2-D is the most common for generator applications.

Key Fuel Properties That Matter

Property
Specification
Why It Matters

Cetane number
Min 45 (EN 590), prefer 50+
Higher cetane = easier starting, smoother combustion, less knock

Sulfur content
Max 10-50 ppm (ultra-low sulfur)
Lower sulfur reduces engine deposits and emissions

Density
0.82-0.845 kg/L at 15 degrees C
Affects energy content per liter; outside this range = poor combustion

Viscosity
2.0-4.5 mm2/s at 40 degrees C
Too thick = poor atomization; too thin = insufficient lubrication for injectors

Water content
Max 200 mg/kg
Water causes corrosion, microbial growth, and injector damage

Lubricity
Min 460 micron wear scar
Protects fuel pump and injector components from wear

Warning: In many developing markets, locally available “diesel” does not meet any recognized standard. I have tested fuel in several countries where the cetane number was as low as 35 and water content exceeded 1,000 ppm. Running a Yuchai generator on this fuel will dramatically increase diesel generator fuel consumption, accelerate wear, and void warranty coverage. Test your fuel supply before committing to long-term operation.

Fuel Grades by Climate

Diesel fuel behaves differently at different temperatures. In cold climates, the paraffin wax in diesel can crystallize, clogging fuel filters and stopping the engine. This is called gelling.

Summer Diesel (ASTM 2-D / EN 590 Class A-F)

Standard diesel for ambient temperatures above 0 degrees Celsius (32 degrees Fahrenheit). This is what you will use in most tropical and subtropical markets — Southeast Asia, Africa, South America, and the Middle East. The cold filter plugging point (CFPP) is typically between -5 and +5 degrees Celsius.

Tesla Power standard specification for most deployments. No special handling required in climates where the temperature stays above 5 degrees Celsius.

Winter Diesel (ASTM 1-D / EN 590 Class 0-1)

Refined to resist gelling at temperatures as low as -20 to -44 degrees Celsius. It has a lower viscosity and lower energy density than summer diesel, which means slightly higher fuel consumption (about 2-3% more per kWh).

If your Yuchai diesel generator operates in cold climates (Central Asia, Northern Europe, high-altitude locations), you must switch to winter-grade diesel before temperatures drop. Some operators blend kerosene with summer diesel as a cost-saving alternative, but this should not exceed 20% kerosene ratio.

Biodiesel Compatibility

This comes up more often than you might think, especially as sustainability becomes a bigger priority for many organizations. Here is the straight answer about biodiesel and Yuchai generators:

B5 (5% biodiesel)
Fully Approved

Requires no modifications. No noticeable performance difference. Widely available in many markets as standard diesel blend.

B20 (20% biodiesel)
Conditionally Approved

Generally compatible with most Yuchai engines. May require more frequent filter changes. Check with Tesla Power for your specific model.

B100 (100% biodiesel)
Not Recommended

Requires major fuel system modifications. Material compatibility issues with seals and hoses. Higher fuel consumption. Not covered by standard warranty.

Important considerations for biodiesel blends:

• Biodiesel has approximately 8-10% lower energy density than petroleum diesel, so expect slightly higher diesel generator fuel consumption (volume per kWh)
• Biodiesel is more susceptible to microbial contamination and water absorption — fuel storage management becomes even more critical
• Biodiesel has solvent properties that can loosen deposits in old fuel systems, potentially clogging filters during the first few tank loads after switching
• Change fuel filters more frequently during the first 100 hours after switching to a biodiesel blend
• Reduce biodiesel storage time — B20 should be used within 6 months of production (vs. 12+ months for petroleum diesel)

Tesla Power recommendation: For most applications, B5 is ideal — it reduces emissions with zero operational impact. B20 is acceptable where environmental regulations or corporate sustainability policies require it. Always consult with your Tesla Power service team before switching fuel types.

Fuel Storage: Doing It Right

How you store fuel is just as important as the fuel itself. Poor storage turns good diesel into bad diesel — often within weeks in tropical climates.

The Main Threats to Stored Fuel

• Water contamination: Enters through condensation (temperature changes create moisture inside the tank), poor tank sealing, or contaminated delivery. Water promotes microbial growth and corrodes metal components.
• Microbial growth (diesel bug): Bacteria and fungi thrive at the water-diesel interface. They produce slimy colonies that clog filters, corrode tanks, and degrade fuel quality. This is the number one fuel problem in tropical climates.
• Oxidation: Diesel degrades over time as it reacts with oxygen. After 6-12 months, fuel loses some of its combustion quality. After 18-24 months, it may need testing before use.
• Particulate contamination: Dust, rust, and debris from tank walls or delivery systems. A single tank of contaminated fuel can destroy a set of fuel injectors.

Storage Best Practices

• Design for drainage: Fuel tanks should have a sloped bottom with a drain valve at the lowest point. Drain water from the bottom every 2-4 weeks.
• Keep tanks full: Minimizes the air space where condensation forms. A 90% full tank has much less condensation risk than a 30% full tank.
• Install a fuel polishing system: These systems continuously circulate fuel through filters and water separators, removing contaminants. The investment pays for itself in extended engine life and reduced filter changes. Tesla Power recommends fuel polishing for all installations with bulk storage tanks.
• Rotate fuel stock: Use the oldest fuel first. If you have a bulk tank, run the generator on it regularly rather than letting fuel sit for months.
• Monitor with fuel test kits: Simple water detection paste and microbial test strips cost a few dollars and can save you thousands. Test monthly in hot, humid climates.
• Biocide treatment: Add a diesel biocide to bulk storage tanks every 3-6 months to prevent microbial growth. Products like Biobor JF or FQS are widely available and effective.

What Fuel Additives Are Worth Using?

The diesel additive market is full of products making big claims. Here is what actually works based on field experience with Yuchai diesel generators:

Additive Type
Benefit
Recommended?

Cetane improver
Improves cold starting, smoother combustion
Yes, if your fuel cetane is below 50

Detergent / injector cleaner
Keeps injectors clean, removes deposits
Yes, especially with variable fuel quality

Biocide
Prevents microbial growth in storage
Yes, for bulk tanks in humid climates

Corrosion inhibitor
Protects fuel system components from rust
Yes, particularly for long-term storage

Cold flow improver
Lowers gelling temperature
Yes, if operating near freezing

Stabilizer
Extends fuel storage life
Yes, for seasonal or standby use

Octane booster
Designed for gasoline — irrelevant for diesel
No

Products from Stanadyne, Power Service, and FQS have good track records in the field. Follow the manufacturer’s dosage instructions — more is not better, and overdosing some additives can actually cause problems.

Fuel Quality and Generator Performance: The Numbers

To put the fuel quality impact in perspective, here is data from a Tesla Power field test on a 200 kW Yuchai generator running 8 hours per day:

Metric
Standard Diesel (EN 590)
Poor Quality Local Diesel
Difference

Fuel consumption (L/h at 75% load)
38.2
42.8
+12%

Monthly fuel cost (at $1.00/L)
$9,170
$10,270
+$1,100/month

Exhaust smoke
Light/transparent
Noticeable black smoke
Visible difference

Injector life (estimated)
8,000-10,000 hrs
4,000-5,000 hrs
50% shorter

Oil degradation rate
Normal
30% faster
More frequent oil changes

That $1,100/month fuel penalty adds up to $13,200 per year — more than half the cost of the generator itself. And that is before accounting for the shortened injector life and more frequent maintenance.

Tesla Power: Fuel-Smart Generator Solutions

Tesla Power designs Yuchai diesel generator systems with fuel quality in mind:

• Duplex fuel filtration as standard — primary filter catches water and large particles, secondary fine filter protects injectors
• Water separator integrated into the fuel supply line
• Optional fuel polishing system for installations with bulk fuel storage
• Fuel level monitoring via the DSE controller for remote tracking of consumption and detection of anomalies (possible theft or leaks)
• Technical guidance on fuel quality standards and additive recommendations for your specific operating region

Product range: 16 kW to 1,000 kW, all Yuchai engine series. All units are tested and shipped with EN 590 equivalent fuel specifications documented.

Frequently Asked Questions

Can I use regular diesel from a gas station in my Yuchai generator?

Yes, in most cases. The diesel sold at commercial fuel stations in most countries meets basic quality standards suitable for diesel generator operation. However, for continuous or heavy-duty operation, verify the fuel meets EN 590 or ASTM D975 standards. In some countries, “premium” or “low-sulfur” diesel is available at a slightly higher price and is worth the extra cost for generator use due to its better combustion characteristics and lower deposits.

How long can diesel fuel be stored for a generator?

Standard petroleum diesel can be stored for 6-12 months under good conditions (sealed tank, minimal temperature variation, treated with stabilizer and biocide). In hot, humid tropical climates, reduce this to 3-6 months without active fuel management. With a fuel polishing system operating continuously, storage life can extend to 12-24 months. After long storage, test the fuel (water content, microbial activity, and cetane number) before using it in your Yuchai generator.

What happens if I put gasoline in a diesel generator?

Do not do this. Gasoline has a much lower flash point and different combustion characteristics than diesel. If mixed into the fuel system, gasoline will cause premature ignition (detonation), extreme engine knocking, and potentially catastrophic engine damage. Even a small amount of gasoline (5-10% of the tank volume) can cause serious problems. If accidental contamination occurs, do not start the engine. Drain the tank completely, flush the fuel system, replace all filters, and refill with proper diesel before attempting to restart. Contact Tesla Power for service support if this occurs.

Does diesel fuel expire?

Diesel does not have a hard “expiration date,” but it does degrade over time. The main degradation mechanisms are oxidation (fuel reacts with oxygen, losing combustibility), moisture accumulation (condensation introduces water), and microbial contamination. Degraded fuel burns less efficiently, produces more smoke, and can clog filters. Using a fuel stabilizer additive and maintaining proper tank conditions can significantly extend useful fuel life. Tesla Power recommends implementing a fuel rotation schedule — use stored fuel within 6 months and replenish with fresh fuel.

Can I use cooking oil or waste oil in my Yuchai generator?

No. While waste vegetable oil (WVO) can be used in some modified diesel engines, Yuchai engines are designed for standard diesel fuel and biodiesel blends up to B20. Waste oil contains free fatty acids, water, food particles, and other contaminants that will damage the fuel injection system. Some specialized waste oil conversion systems exist, but they require significant engine modifications and void the manufacturer warranty. For sustainable fuel options, stick with commercially produced B5 or B20 biodiesel blends.

About the Author: This article draws from field experience with fuel quality challenges across Africa, Southeast Asia, and the Middle East. The performance data comes from actual Tesla Power field tests conducted on client installations. For fuel-specific guidance for your operating region, contact Tesla Power.