3 Problems With Your Diesel
(And How to Fix Them)
2 min read
Many diesel truck owners experience the same negative and frustrating pattern with their diesel’s performance over time: lost power and response, declining fuel economy, more smoke and regens, and - in the worst cases - premature component wear and failure (including CP4).
These issues are caused by the poor quality of ULSD at the pump. Fortunately, they are treatable and preventable going forward.
The 3 Root Causes
What's actually wrong with the fuel?
1. No Detergents
Unlike gasoline, ultra-low sulfur diesel (ULSD) isn’t required to contain detergents. As a result, internal diesel injector deposits (IDIDs) and nozzle-tip coking build up over time. Spray pattern distorts, atomization suffers, combustion quality drops, and soot rises.
2. Low Cetane
Typical U.S. pump diesel tests around 42 to 45 cetane. Most light‑duty diesels operate effectively from 48 to 50 cetane. When cetane is low, ignition lags behind injection, the burn starts late, more fuel is wasted as heat and soot, and you feel the loss in power and economy.
3. Insufficient Lubricity
The U.S. ULSD limit allows a 520 μm wear scar diameter (ASTM D6079), but Bosch’s CP4 guidance is 460 μm or less. Untreated fuel sits outside the pump’s protection target, increasing wear and the likelihood of costly pump/injector damage.
What Drivers Experience
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Reduced power and slower response in daily driving and under load
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Lower MPG than expected for the vehicle
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More frequent DPF regens and visible smoke on acceleration
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Higher wear risk in high-pressure components; possible CP4 failure
The Two-Step Fix
Archoil AR6400-D Diesel Fuel System Cleaner removes internal diesel injector deposits and nozzle-tip carbon to restore precise spray pattern and fueling; helps reduce smoke and carbon loading to DPF/turbo/EGR.
Archoil AR6500 Diesel Treatment raises cetane into the correct operating band, keeps injectors clean between deep cleans, and adds lubricity protection for critical High-Pressure Common Rail components.
Proof in Operation
Restore Injectors
AR6400-D contains a strong dose of highly concentrated detergents which quickly remove internal diesel injector deposits (IDIDs) and heavy carbon build-up from injector tips. Use of AR6500 maintains injectors at every fill-up for maximum performance.
Cetane Uplift
AR6500 typically adds 4 to 5 cetane points (up to 8, depending on treat rate). In practice, that takes average pump diesel from 42–45 CN to roughly 48–50 CN, reducing ignition delay to OEM‑calibrated levels and improving combustion stability, torque response, cold‑start performance and fuel economy.
Lubricity Protection
In testing, AR6500 reduced wear-scar from 615 μm to 348 μm (ASTM D6079), easily surpassing the ~460 μm protection target Bosch specifies for CP4 pumps, providing added margin for HPCR durability.
Documented MPG Gain
On a defined route under comparable conditions, MPG improved by 11.1% after one tank with AR6400‑D followed by AR6500 every fill.
Outcomes vary with baseline deposits, fuel, and duty cycle.
What To Expect
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Fuel economy increasing back toward factory figures
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Sharper throttle response and stronger pull and acceleration under load
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Smoother idle, cleaner exhaust and less smoke
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Fewer regens and reduced stress on DPF/EGR/turbo components
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How to Use
First tank:
Add one 12 oz bottle of AR6400-D to ~40 gallons of diesel. Drive normally.
Every tank after that:
Add AR6500 at 1 oz per 10 gallons of diesel. One 40 oz bottle treats 400 gallons.