1994-1998 Dodge 5.9L Cummins Fuel Additives

Fuel additives and the 1994-1998 Dodge Ram 5.9L Cummins

The Bosch P7100 on the 12-valve Cummins is a mechanical inline pump. Its governor side is lubricated by engine oil, which is why low fuel pressure doesn't destroy it the way it destroys a VP44. The plungers and barrels are a different story: the fuel itself lubricates them. Our research didn't turn up a platform-specific additive requirement for this engine. Lubricity and anti-gel treatments are general diesel practice, not something documented as a 12-valve requirement. Treat an additive as your call, based on how and where you run the truck.

What an additive won't fix

If your 12-valve starts hard, idles low or feels down on power, check the hardware before you reach for a bottle. The usual causes are a worn mechanical lift pump, a weak overflow valve on the P7100, a clogged pre-strainer in the fuel heater, or air getting in through a hardened rubber return hose under the intake manifold. None of those respond to a treatment. Get the fuel system sound first, then decide on an additive.

How to choose

Pick by the job you want done.

• Routine fill-ups: everyday treatments and lubricity products.
• Occasional cleanup: cleaners and cetane boosters for treating a tank now and then.
• Cold weather: anti-gel and winter blends. Around our shop in Wildwood, FL that mostly matters for trucks that travel north or spend the winter there.

What we carry

Hot Shot's Secret Everyday Diesel Treatment, Diesel Extreme, LX4 Lubricity Extreme, EDT + Winter Defense, Diesel Winter Anti-Gel and Diesel Winter Rescue Emergency. Lucas Oil Fuel Treatment, Anti-Gel Cold Weather Diesel Treatment, Diesel Deep Clean and Cetane Power Booster. Alliant Power ULTRAGUARD, WINTERGUARD and LUBRIGUARD diesel fuel treatments. Exergy diesel additive in 4 oz and 16 oz bottles, regular and winter blend, including cases of 12. XDP Diesel Power Plus and Merchant Automotive diesel fuel additive. The full lineup is on our fuel additives page.

Fitment notes

Additives are dosed by the tank, not fitted to an engine, so read each label for the dose and confirm it's meant for diesel. The fitment that matters is the rest of your fuel system. A 1998 can be a 12-valve or a 24-valve: the 12-valve has the P7100 inline pump with a shutoff solenoid on top, and the pump lubrication notes on this page are written for it. Not sure which you have? Verify by VIN.

Frequently asked questions

Does the P7100 need a lubricity additive?

We haven't found a documented requirement. The governor side runs on engine oil and the plungers are lubricated by the fuel. Lubricity additives are a general diesel practice, not a 12-valve-specific rule, so it's your call.

Can an additive fix low power or a hard start?

Don't count on it. On a 12-valve those symptoms usually trace to the lift pump, the overflow valve, a clogged pre-strainer or an air leak at the return hose. Fix the hardware first.

Which products here are for cold weather?

Look for anti-gel or winter on the label: Hot Shot's Secret Diesel Winter Anti-Gel and EDT + Winter Defense, Lucas Oil Anti-Gel Cold Weather Diesel Treatment, Alliant Power WINTERGUARD and the Exergy winter blend. Hot Shot's Secret Diesel Winter Rescue is labeled as an emergency product.

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.