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Call or Text (352) 722-5295Fuel Additives on the 2004.5-2007 RAM 5.9L Cummins
Everything in the tank of a 5.9L Cummins ends up in a Bosch CP3 and six solenoid injectors. The CP3 builds 4,251 to 23,206 psi in the rail, and its cascade overflow valve routes part of the low-pressure fuel to lubricate the pump itself. At those pressures, particles in the fuel get more abrasive, not less. That is why fuel quality matters so much on this engine.
What fails and why
Fuel contamination, mainly water and dirt, is the leading cause of early injector death on these trucks, and lubricity and anti-water additives are the preventive. Water also rusts the injector connector tubes and sends the rust into the injectors.
Additives play a part in diagnosis, too. A sticking Fuel Control Actuator (FCA) on the back of the CP3 causes a rattle at idle, surging, rough idle, stalling and hard starts. If a dose of ashless two-stroke oil makes the truck run clean until the additive is used up, the FCA is the likely culprit, and replacing the actuator is the fix.
Choosing a treatment
Pick by the job you need done:
- Lubricity: Hot Shot's Secret LX4 Lubricity Extreme and Alliant Power LUBRIGUARD.
- Cold weather: Hot Shot's Secret Diesel Winter Anti-Gel, EDT + Winter Defense and Diesel Winter Rescue Emergency, Alliant Power WINTERGUARD, Lucas Oil 10865 Anti-Gel Cold Weather Diesel Treatment and Exergy Winter Blend.
- Cleaning and cetane: Lucas Oil Diesel Deep Clean and Lucas Oil Cetane Power Booster.
- General treatments: Hot Shot's Secret Everyday Diesel Treatment and Diesel Extreme, Alliant Power ULTRAGUARD, Exergy Performance diesel additive, XDP Diesel Power Plus, Merchant Automotive 10508 and Lucas Oil 10003 Fuel Treatment.
An additive protects; it does not repair. If a return-flow test shows a single injector flowing over 40 ml per minute, that injector needs replacing.
What we carry
Treatments from Hot Shot's Secret, Exergy Performance, Lucas Oil, Alliant Power, XDP and Merchant Automotive. Exergy offers 4 oz and 16 oz bottles in regular and Winter Blend, with case-of-12 packs that suit a shop or a fleet. See every brand in our fuel additives collection.
Fitment notes
Additives are not matched by part number the way injectors are, but follow the dose on each bottle for your tank size. The 2006 Ram 2500 is listed with a tank of about 35 gallons, and Chrysler references both 34- and 35-gallon tanks on these trucks. An additive does not replace the factory filter change every 15,000 miles or 12 months, and the water-in-fuel sensor in the filter canister is still your warning for water. 2007 shares the model year with the 6.7L, so if you are buying other fuel parts at the same time, verify your engine by VIN.
Frequently asked questions
Can I put two-stroke oil in my 5.9L Cummins fuel?
Ashless two-stroke oil is used as a diagnostic on this engine. If a rattle at idle, surging or stalling clears up after a dose and comes back once it is gone, the FCA is sticking and should be replaced. For ongoing protection, use a purpose-made diesel lubricity treatment.
What should I never add to the fuel?
Never add used motor oil, ATF or so-called mouse milk to the fuel on a common-rail 5.9L. Clearances in the pump and injectors are about 25 millionths of an inch, and particulates become more abrasive as rail pressure rises.
Will an additive fix a bad injector?
No. Additives help prevent the water and dirt damage that kills injectors early, but a worn or cracked injector has to be replaced. Run a return-flow test first; total return over 180 ml after a minute at idle, or any single injector over 40 ml per minute, points to injector or connector tube trouble.
Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.