DIESEL FROM THE PUMP IS HARMING YOUR ENGINE

2 min read

Today’s Ultra-Low Sulfur Diesel (ULSD) has far less lubricity than traditional diesel. The refining process that removes sulfur also strips away natural lubricating compounds, leaving the fuel “drier”, increasing metal-to-metal contact and accelerating wear in critical engine components.

This increases the risk of premature failure in critical components such as injectors and high-pressure fuel pumps – most notably the widely used Bosch CP4 has become well-documented for this issue.

Why U.S. Fuel Standards Fall Short

  • Lubricity is measured by wear scar diameter (smaller is better)

  • U.S. legal limit: up to 520 µm

  • Manufacturer recommendation: 460 µm or below

  • Typical diesel from the pump is closer to 500 µm, which increases risk of premature failure

Even fuel that meets legal U.S. standards can be unsafe for your fuel pump

Why The CP4 Fails

and the catastrophic impact it can have on your entire fuel system

  • Designed for ~460 µm fuel, but often exposed to ~500 µm fuel (or worse)

  • The steel cam and pistons grind, rapidly accelerating wear, sending metal shavings through entire fuel system

  • Fuel filters become overwhelmed and unable to stop the spread of debris – this is commonly referred to as the CP4 "grenading"

When the CP4 fails, the whole system goes with it

Pump, injectors, rails, filters, and tank all need replaced. Repairs often reach $8,000–$10,000.

CP4 Pumps Fail More in the U.S.

The Bosch CP4 pump isn’t inherently doomed to fail. In fact, it operates far more reliably in Europe. The difference comes down to the fuel

  • European diesel has stricter lubricity standards, with wear scar limits set to 460 µm, matching Bosch’s design specification

  • In the U.S., ULSD is legally allowed up to 520 µm. This creates a dangerous lubricity gap that pushes the CP4 outside its safe operating range

Same Pump. Different Fuel.

In Europe, CP4 failures are reported at well under 1%, thanks to stricter lubricity standards.

Failure rates in the U.S. have been documented as high as 7% — that’s about 1 in 14 trucks.

Same Pump. Different Fuel.

In Europe, CP4 failures are reported at well under 1%, thanks to stricter lubricity standards.

Failure rates in the U.S. have been documented as high as 7% — that’s about 1 in 14 trucks.

The Simple Fix

Archoil AR6500 Diesel Treatment

The simplest way to eliminate the risk of low-lubricity diesel is to treat your fuel at every fill-up with a proven additive that restores the protection ULSD is missing. For high-pressure systems like the CP4, lubricity isn’t optional — it’s essential. Archoil AR6500 Diesel Treatment delivers industry-leading protection where it matters most.

In independent testing

AR6500 Reduced Wear By 43%

Wear Scar Before

Base fuel: 614.5 microns (µm)

Wear Scar After

Fuel with AR6500: 347.5 µm

What is the test for lubricity?

ASTM D6079 – High Frequency Reciprocating Rig (HFRR) Test

The HFRR test measures lubricity by oscillating a metal ball against a metal plate while immersed in fuel. Afterwards, the size of the wear scar on the ball is measured — the smaller the scar, the better the fuel protects against wear.

AR6500 reduced the wear scar of low quality diesel from 614.5 µm all the way down to just 347.5 µm. That's not just compliant, but well below even the strictest manufacturer recommendations – providing far greater protection for your fuel pump and injectors than what standard ULSD alone can offer.

The Only Additive Your Diesel Needs

AR6500 is a complete diesel treatment. In addition to outstanding wear protection, it improves fuel quality across the board:

  • Boost cetane up to 8 points for smoother combustion, faster cold starts, and better fuel economy

  • Clean injectors and maintain a clean fuel system and post-combustion system (turbo and DPF) with advanced detergents

  • Improve diesel fuel economy 6-10%+

  • Fewer regens, less soot and smoke, and a quieter, more efficient engine

⏳ use code

MAXIMIZE

at the checkout for 20% off AR6500

Treat your diesel every tank 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.

AR6500 Diesel Treatment
AR6500 Diesel Treatment
AR6500 Diesel Treatment
AR6500 Diesel Treatment
AR6500 Diesel Treatment
AR6500 Diesel Treatment
AR6500 Diesel Treatment
AR6500 Diesel Treatment
AR6500 Diesel Treatment
AR6500 Diesel Treatment

AR6500 Diesel Treatment

$44.95
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Shipping calculated at checkout.
  • Reduce wear up to 43% (ASTM D6079)
  • Raise cetane up to 8 points
  • Clean and maintain injectors, the turbo and DPF (reduces regens)
  • Maximize power, performance & MPG
  • 100% Money Back Guarantee
  • Free U.S. shipping on orders over $40

AR6500 is for use at every fill-up.

Treat Rate: 1oz per 10 gallons of diesel

Our bottle features a handy measuring chamber for easy, accurate dosing.

Biodiesel naturally adds lubricity, but it’s not consistent enough to count on. In colder months, suppliers often reduce or remove biodiesel blends to prevent gelling, leaving fuel just as “dry” as standard ULSD.

In some regions, renewable diesel is used instead. Because it has almost no natural lubricity, refiners add additives before distribution, but only enough to meet the U.S. minimum standard of 520 µm, which many manufacturers still consider inadequate.

While transmission fluid contains lubricants, it was never meant to be burned – and doing so can cause serious problems in modern diesels.

Burning transmission fluid introduces ash, heavy metals, and chemical residues into the fuel system that can clog the injectors and DPF, harm combustion, and cause long-term engine damage.