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The Role of Lubricants in Diesel Engines

The Role of Lubricants in Diesel Engines

Why Engine Oil Is More Than Just a Fluid

In the commercial trucking industry, diesel engines are the workhorses that drive everything from urban delivery vans to long-haul 10-ton trucks. To keep these engines running smoothly, one element is absolutely essential: lubricant oil. Far beyond just “oil,” engine lubricants are critical for performance, durability, and reliability—especially in used Japanese trucks operating in demanding environments.

1. What Does Lubricant Oil Do in a Diesel Engine?

Lubricants in diesel engines serve five essential functions:

  1. Reduce friction between moving parts

  2. Prevent wear by creating a protective film

  3. Clean the engine by suspending dirt and combustion particles

  4. Cool components by carrying away excess heat

  5. Seal small gaps between piston rings and cylinder walls to maintain compression

Without proper lubrication, even the most robust Japanese diesel engines—like the 6D15, 4M51, or 6UZ1—can suffer from premature wear and failure.

2. Why Lubricants Matter More in Diesel Trucks

Diesel engines operate at higher compression ratios and torque levels than gasoline engines, leading to:

  • Higher temperatures

  • Greater stress on engine components

  • More soot and combustion by-products

This makes lubricant selection and maintenance even more important in heavy-duty commercial trucks, especially when exporting to regions with hot climates or poor road conditions.

3. Types of Diesel Engine Lubricants

There are three main types of engine oils used in diesel trucks:

Type Characteristics Best for…
Mineral Oil Affordable, natural base Older engines, short-haul trucks
Synthetic Oil Enhanced protection, long life Modern engines, long-distance use
Semi-Synthetic Mix of mineral and synthetic Balanced performance and economy

Example:

  • Isuzu Giga with 6UZ1 engine: Recommended synthetic for extended oil change intervals.

  • Hino Ranger with H07D engine: Semi-synthetic or mineral, depending on usage and mileage.

4. What Happens Without Proper Lubrication?

Neglecting lubricant maintenance can lead to:

  • Increased engine friction and heat

  • Metal-to-metal wear

  • Sludge build-up

  • Decreased fuel efficiency

  • Engine seizure or failure

These issues are costly to repair and often avoidable with regular oil checks and timely replacement.

5. Real-World Example: Lubrication Saves a Fleet in Kenya

A logistics company in Kenya imported several used Mitsubishi Fuso Fighters (6M61 engine). At first, they used low-grade oil to cut costs. After two trucks suffered from engine overheating, they switched to high-quality synthetic diesel oil and saw immediate results.

“EVERYCAR.jp advised us on oil selection and intervals. Since we changed our approach, our trucks run cooler and require fewer repairs. It made a huge difference.”

6. What Exporters Should Do

For Japanese used truck exporters, it's smart to:

  • Include last oil change date and oil type in inspection reports

  • Mention recommended lubricant grade (e.g., 15W-40, 10W-30)

  • Note if oil filters have been replaced

  • Recommend first oil change timing after import (especially if shipping took time)

This not only builds buyer trust but helps protect the engine during its critical early use in a new country.

7. What Buyers Should Ask

When importing a used diesel truck, ask:

  • What type of oil was used in Japan?

  • When was the last oil and filter change?

  • What grade of oil is suitable for local temperature and road conditions?

Pro Tip: Hot regions like the Middle East or Africa often require higher-viscosity oils (e.g., 20W-50) for better thermal stability.

Conclusion

Lubricants are the invisible protector of diesel engines. They reduce wear, enhance efficiency, and extend engine life—making them one of the most cost-effective forms of maintenance. Whether you operate a 2-ton flatbed or a 12-ton dump truck, choosing and maintaining the right oil is crucial for safe and profitable operations.

At EVERYCAR.jp, we don’t just sell trucks—we help you understand and maintain them. From engine specs to oil recommendations, we give you everything you need to keep your truck running strong, wherever it’s headed.

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