The Diesel at U.S. Pumps Is Too Dry for Your Fuel Pump (And the 11¢ Fix)
Today's ultra-low sulfur diesel lost its natural lubricity in refining. Your high-pressure fuel pump is paying for it — and if you're running a Bosch CP4, the bill can reach five figures.
The Lubricity Gap, in Four Facts
- 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 pump diesel: closer to 500 µm
Even fuel that meets legal U.S. standards can be unsafe for your fuel pump. That gap between what's allowed and what your pump was designed for is doing damage at every mile.
Your high-pressure fuel pump is lubricated by the fuel itself. The refining process that removes sulfur from modern diesel also strips away its natural lubricating compounds, leaving the fuel "drier" — increasing metal-to-metal contact and accelerating wear in critical components.
The result is a rising risk of premature failure in injectors and high-pressure fuel pumps — most notably the widely used Bosch CP4, which has become well-documented for exactly this issue. Here's how it happens.
Refining Stripped the Lubricity Out
Removing sulfur to meet ULSD standards also removed the compounds that used to protect fuel-lubricated components. The fuel your truck runs on today is drier than anything these pumps were engineered around — and U.S. standards don't require it to be fixed.
The CP4 Was Built for Better Fuel
The CP4 is designed for ~460 µm fuel but is routinely exposed to ~500 µm fuel — or worse. The steel cam and pistons grind, rapidly accelerating wear and sending metal shavings through the entire fuel system. Filters become overwhelmed and can't stop the spread — this is what's commonly called the CP4 "grenading."
Wear scar diameter (ASTM D6079) — lower is better.
Same Pump. Different Fuel.
The CP4 isn't inherently doomed — it operates far more reliably in Europe, where diesel lubricity standards are stricter (460 µm, matching Bosch's design spec). There, CP4 failures are reported at well under 1%. In the U.S., where 520 µm is legal, failure rates have been documented as high as 7% — about 1 in 14 trucks.
Documented CP4 failure rates. The difference comes down to the fuel.
When the CP4 Goes, the Whole System Goes With It
A grenaded pump doesn't fail alone — it sends metal debris through everything downstream. Pump, injectors, rails, filters, and tank all need replaced:
Protection costs 11¢ per gallon.And it doesn't just protect — it improves performance and fuel economy at the same time.
Put the Lubricity Back. Every Tank.
The gap between U.S. pump fuel and what your pump was designed for is treatable at every fill-up — no tools, no shop visit, no change to how you drive.
Treat Every Fill-Up With AR6500
AR6500 Diesel Treatment restores the lubricity modern ULSD is missing, helping protect injectors, pumps, and other critical components. Add 1 oz per 10 gallons at every fill-up — the bottle's built-in measuring chamber makes dosing easy, and one 40 oz bottle treats 400 gallons.
AR6500 Reduced Wear by 43%
Wear Scar Before
Base fuel: 614.5 microns (µm) — well outside even the legal U.S. limit, let alone the manufacturer recommendation.
Wear Scar After
Fuel with AR6500: 347.5 µm — not just compliant, but well below even the strictest manufacturer recommendations, providing far greater protection than standard ULSD alone.
What the Test Measures
The ASTM D6079 HFRR test oscillates a metal ball against a metal plate immersed in fuel, then measures the wear scar left on the ball. The smaller the scar, the better the fuel protects against wear.
Independent ASTM D6079 testing. Outcomes vary with baseline fuel quality and duty cycle.
Treat Every Tank and You'll Also Get
- Cetane boosted up to 8 points — smoother combustion, faster cold starts
- Injectors, turbo and DPF kept clean by advanced detergents
- Diesel fuel economy improved 6–10%+
- Fewer regens, less soot and smoke, and a quieter, more efficient engine
"I use Archoil every fill up. 287,000+ miles on my 2011 Sierra Denali HD Duramax with the original CP-4 fuel pump, injectors, & turbo."
— Bradley M., verified buyer · 2011 Sierra Denali HD Duramax
"I was not really concerned about an increase in fuel mileage but was worried about the lack of lubricity of the ULSD in use today. But I got an increase in my city mileage of about 2 mpg — on the road it translates to a 3 mpg increase."
— Stewart J., verified buyer
"Loving using Archoil in my 2026 Silverado 2500 HD. Since making the switch from Hot Shots, I've noticed better MPG and engine performance in a matter of weeks. Going on year three of using this product and never looking back!"
— Eric M., verified buyer · 2026 Silverado 2500 HD
AR6500 Diesel Treatment
- Reduce wear up to 43% (ASTM D6079)
- Raise cetane up to 8 points
- Clean and maintain injectors, the turbo and DPF (reduces regens)
- Treats 400 gallons — just 11¢ per gallon
- Free U.S. shipping on orders over $40
For every diesel. Power Stroke, Cummins, Duramax, European diesels, ag & commercial equipment up to Class 8 — pre-emissions, emissions-equipped or deleted, running ULSD, renewable diesel or bio blends.
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100% Money Back Guarantee. No questions asked — if you're not satisfied with overall product performance, return it for a full refund.
Common Questions
Which trucks does this work on?
Every diesel. AR6500 is compatible with all diesel vehicles and equipment: Power Stroke, Cummins, Duramax, European diesel cars and SUVs, light- and medium-duty trucks, agricultural equipment, commercial vehicles, and heavy trucks up to Class 8.
It can be used in pre-emissions, emissions-equipped and deleted engines, and is compatible with ULSD, renewable diesel and biodiesel blends.
How do I use AR6500?
Add AR6500 at every fill-up at 1 oz per 10 gallons of diesel. The bottle features a handy measuring chamber for easy, accurate dosing, and one 40 oz bottle treats 400 gallons.
How fast will I feel a difference?
Cetane and lubricity benefits are in effect from the first treated fill-up. AR6500's detergents then keep working at every tank, cleaning the injectors and maintaining combustion quality as you drive.
Will this protect my CP4 pump?
Yes — lubricity protection is central to AR6500's formulation. In ASTM D6079 testing it reduced wear scar from 615 μm to 348 μm, comfortably inside the ≤460 μm target recommended by the Engine Manufacturers Association and specified by Bosch for CP4 protection. That protection is active from the first treated tank.
Doesn't biodiesel add lubricity?
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.
Can't I just use transmission fluid?
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.
Why not just use a cheaper additive?
AR6500 is a complete treatment. It addresses all fuel problems at once: detergency, cetane and lubricity, at levels that exceed the competition. A single dose at every fill-up covers everything the fuel is missing.
Can I mix it with other additives?
We don't recommend mixing AR6500 with other additives. The formulation contains no fillers and already carries the optimal amounts of cetane, detergency and lubricity — there's nothing to gain by stacking anything else in the tank.
Do I need to change my filters or oil?
No. AR6500 works entirely within the fuel system, so no oil change is needed. A fuel filter change isn't required either: at the every-tank treat rate, cleaning is gradual, so filters aren't put under the load a concentrated clean-up can create.
Will this affect my warranty?
Archoil products will not void your warranty. AR6500 is an in-tank fuel treatment used by owners of trucks in and out of warranty every day. No Archoil product contains alcohol, which some owner's manuals specifically caution against in fuel additives. If you have any specific warranty concerns, please consult your vehicle manual.
How fast does it ship?
Orders ship from our Connecticut warehouse via UPS or USPS — orders placed on business days typically dispatch within 1 business day, with delivery in 2–5 business days depending on location. Expedited shipping is available at checkout. Free U.S. shipping on orders over $40.
Your Pump Runs on the Fuel You Give It.
Restore the lubricity it was designed for — at every fill-up, for 11¢ a gallon.
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