If you own a diesel truck, there’s a hidden threat lurking in your fuel tank - a severe lack of lubricity in the fuel. Today’s Ultra-Low Sulfur Diesel (ULSD) in the U.S. is often “dry” fuel that doesn’t provide enough lubrication for critical engine components. That’s because the refining process used to remove sulfur also strips out many of the natural lubricants found in diesel. Without those compounds, the resulting fuel lacks the “slickness” needed to protect metal-on-metal contact in high-pressure systems. Over time, running on fuel with insufficient lubricity can lead to accelerated wear, metal shavings in your fuel system, and even a catastrophic (and extremely expensive) fuel pump failure.

U.S. Fuel Standards Are Leaving Your Engine Exposed

The problem is that U.S. diesel fuel standards allow much lower lubricity than what modern high-pressure fuel pumps need. Fuel lubricity is measured by wear scar diameter – smaller scars mean better lubrication. American ULSD can legally have a wear scar up to 520 microns (µm), but many engine manufacturers insist it should be closer to 460 µm for reliable pump protection. In plain terms, U.S. diesel can be far less “slick” than the fuel these pumps were designed for. Diesel that just meets the U.S. legal limit would be considered problematic by manufacturer standards, creating a lubricity gap that spells trouble for modern fuel systems.

Why the CP4 Pump Fails - and What It Costs

The Bosch CP4 high-pressure fuel pump, found in many modern diesel pickups, is especially vulnerable to low-lubricity fuel. Unlike older pumps, the CP4 relies entirely on diesel fuel for lubrication - it has no oil sump. Bosch engineered it for fuel with a wear scar of around 460 µm, but U.S. pump diesel often lands around 500 µm, or worse, which is outside the pump’s safe operating range.

Without adequate lubricity, the CP4’s steel cam and pistons experience metal-on-metal contact. Wear accelerates quickly. In many cases, the pump “grenades” - it self-destructs internally, sending metal shavings throughout the fuel system. These particles contaminate the injectors, fuel rails, regulators, and even the tank. The fuel filter catches some debris, but during a failure it quickly becomes overwhelmed. The damage spreads fast, and the result is a total system compromise.

Fixing a CP4 failure isn’t just painful, it’s brutally expensive. A full repair often means replacing the pump, injectors, filters, lines, and flushing or even replacing the fuel tank. It’s not unusual for the total bill to exceed $8,000–$10,000. All from one tank of overly “dry” diesel.

Biodiesel? Sometimes Helpful, Not Always Reliable

While small biodiesel blends can improve lubricity, they’re not a consistent safeguard. In colder weather, many suppliers reduce or remove biodiesel to prevent gelling. And in some regions, renewable diesel is used instead – which has very poor lubricity unless heavily treated. You simply can’t rely on biodiesel being present year-round or nationwide.

The Simple Fix: Lubricity You Can Count On

There’s a simple, affordable way to eliminate the risk of low-lubricity diesel — treat your fuel at every fill-up with a proven additive that restores the protection your fuel is missing. But not just any additive will do - especially when it comes to protecting high-pressure systems like the CP4, lubricity is non-negotiable - and Archoil AR6500 Diesel Treatment delivers industry-leading performance where it matters most.

In independent ASTM testing, AR6500 reduced a poor fuel’s wear scar from 614 µm all the way down to just 347 µm - not just compliant, but well below even the toughest manufacturer recommendations. That level of lubricity creates a cushion of protection for your fuel pump and injectors that standard ULSD simply can’t match.

Why AR6500 Is the Only Additive You Need

Unlike basic lubricity additives or single-function cetane boosters, AR6500 is a complete diesel treatment. In addition to outstanding wear protection, it improves fuel quality across the board:

• Up to 8 points of cetane boost for smoother combustion, faster cold starts, and better fuel economy
• Advanced detergents that clean injectors and maintain a clean fuel system and post-combustion system (turbo and DPF)
• Fewer regens, less soot and smoke, and a quieter, more efficient engine

Every feature of AR6500 was engineered to solve real-world diesel problems.

Conclusion: Solve the Lubricity Gap for Good

Low-lubricity fuel is one of the biggest threats to modern diesel engines and it's baked into nearly every gallon of ULSD sold in the U.S. But with Archoil AR6500 Diesel Treatment, you can close that gap completely.

Treat your diesel every tank, every time, and you’ll protect your fuel system from wear, extend the life of critical components, and gain noticeable improvements in performance, fuel economy and reliability. It’s not just smart, it’s essential protection for anyone who wants their diesel to last.