The Best Diesel Fuel Additives Keep Your Engine Running

Evan Williams
by Evan Williams
Diesel fuel goes bad with time, but additives can make it last longer and improve performance. Photo credit: David Traver Adolphus / AutoGuide.com.

If your diesel car, truck, or even farm equipment isn’t running right anymore or is sitting parked for a long time or in long temperatures, then diesel fuel additives might be exactly what you need to keep it in top form.

With fuel additives for summer, winter, filter cleaning, de-icing, and to stop fungus from growing in your tank, the best diesel fuel additives offer choices for just about any situation you might face when it comes to compression ignition engines. They’ll help clean your fuel, your engine’s important fueling components, and even the tank itself to keep everything running right.

For more information on the best diesel fuel additives, refer to our table of contents.

1. Editor's Pick: STA-BIL Diesel Fuel Stabilizer

You've likely already heard of STA-BIL for its gasoline engine products, be that a car you park for the winter or your lawn and garden gas-powered equipment. But the company makes a fuel stabilizer for diesel engines too.

As diesel fuel ages, it can oxidize, gather bacteria, and even grow fungus. STA-BIL diesel formula fuel stabilizer works to bond with that water, keeping the fuel fresh in the tank for up to a year. That means fewer worries about starting your engine after it's been parked for a long time. Ideal for seasonal diesel engine use, say a farm truck that sits much of the winter or your diesel RV.

This recommendation won't prevent gelling, so if your diesel needs to start in the extreme cold you might look into STA-BIL's other winter-specific products. The fuel treatment also can be used with every tank in order to help clean and lubricate your fuel system. It's safe for diesel and biodiesel fuels.

Pros

Keeps diesel from growing fungus and keeps it fresh, ideal for seasonal engine use

Cons

Doesn't contain anti-gel for winter

2. Howes Diesel Treat

Howes Diesel Treat advertises that it's safe for all diesel fuel systems, and even works in your home heating oil tank to help treat ultra-low-sulfur diesel issues and fight gelling. On top of preventing gelling, it helps to separate the water in your fuel system, removing the water from the fuel safely and helping your engine to run better.

Howes says that its formula also works to add lubricity to fuel injectors, pumps, and the upper cylinder liners, which should add to engine performance and durability for those concerned with ULSD fuels currently in use. The company recommends blends for both summer performance enhancement and winter use when anti-gel is even more critical to fuel system performance and cold-weather starting. It can also help to reduce smoking and rough idle in diesel engines where buildup is affecting performance, and the manufacturer says it is particulate filter friendly, essential for modern diesels.

Pros

Stops fuel gelling, adds lubricity, particulate filter friendly

Cons

Doesn't offer cetane boost

3. Power Service Diesel Kleen + Cetane Boost

Another warm/cool weather diesel fuel additive, the Power Service Diesel Kleen Max HP formula is designed to clean injectors and lubricate the components of the fuel system, making it ideal for older models running on modern fuel.

Power Service says it'll boost your fuel economy up to eight percent and can restore lost power and smooth out a rough engine, thanks to cleaning out deposits that are making your fuel system not perform like it used to. This option also has a cetane booster, which is like the diesel equivalent of octane. More cetane helps minimize the time between when the fuel is injected and when it ignites. So a higher number fuel ignites more easily and readily when the engine compresses the air fuel mixture and that can help lead to more complete combustion. It can also make for quicker starting and improved fuel economy.

One container treats up to 250 gallons of diesel.

Pros

Improves fuel economy, adds cetane, restores lost power

Cons

Needs additional additives below 30 degrees

4. Stanadyne Diesel Performance Formula

Stanadyne Diesel Performance Formula's additive is designed to help your engine run better. That's thanks to detergent in the bottle that works to clean the injection system to help it run better.

The manufacturer says independent testing shows a four-percent average fuel economy improvement with the additive. It cleans and protects, with modifiers to help protect parts like your injection pump and nozzles, while the alcohol-free formula avoids corrosion, water absorption, and accelerated wear. The formula is compatible with up to 20-percent biodiesel for cleaner fuel use.

If your fuel is at risk of gelling, this product can raise the gel point of diesel by up to 40 degrees, while improving the ice-up temperature of your fuel filter by 25. That can be the difference between starting and staying in the morning for drivers who need to be going. Lastly, by helping clean your engine, it can help reduce smoke and emissions.

Pros

Cleans injection system, improves fuel economy, alcohol-free formula

Cons

Comes in a small container if you're looking at commercial use, fuel economy improvements may vary

5. Ford Motorcraft Cetane Booster

Who knows exactly what fuel additives your vehicle might need as it ages? The company that engineered, designed, and built it, that's who. So go straight to the source of your Ford Power Stroke diesel for this Motorcraft Cetane Booster and Performance Improver.

It's designed for your Ford, as well as to work with diesel engines to combat the effects of low-quality diesel. It also boosts the cetane rating to help starting performance and works to make your engine run more smoothly. The extra lubricity added to the fuel works to reduce engine wear. The fuel additive from Ford's parts arm, Motorcraft, doesn't use alkyl nitrates that can degrade your fuel over time. Instead, it helps with fuel stability and stops algae growth. That can make your truck run better while also helping your diesel tank to stay corrosion free for longer. It's also offered in three sizes to suit your needs.

Pros

Made by and for Ford diesel engines, helps fuel stability, stops algae growth, offered in various sizes

Cons

Not an anti-gel formula

6. Power Service Diesel 911

Power Service Diesel 911 is designed for diesel owners and drivers who should have already used a fuel additive but didn't. It's designed to help get you out of the jam from fuel lines that are already gelled up.

Diesel fuel gels when the temperatures drop below freezing. Paraffin wax, a normal part of diesel fuel, begins to crystallize at low temperatures, first becoming cloudy, then turning your tank into jelly. This is not a preventative, for that they make other additives, but it's instead ready for winter emergencies. Not only will it work to ungel the diesel fuel that's already clogging up your fuel lines and injectors, but it will also de-ice frozen fuel filters to get you back on the road.

The manufacturer says it's perfect for when you can't start in the cold, or when the engine won't make power because of gelled diesel. Once it's liquid again, you can add another additive to make sure that the fuel doesn't turn back into a gel.

Pros

Ungels already gelled diesel, designed for winter emergencies, de-ices frozen fuel filters

Cons

Won't stop it from happening again, will need other additives for performance

7. Star Brite Star Tron Gas Tank & Fuel System Cleaner

Over time, the fuel tank itself can become part of the rough-running problems with your diesel. Corrosion can build up on the walls of the tank thanks to water in the fuel, while old fuel, sitting, and contaminants that enter either through the fuel or through the open tank lid can build up in a sludge that lines your tank and clogs lines and filters.

Star Brite's Star Tron is a fuel tank cleaner, designed with proprietary enzymes that dissolve and break down the sludge, varnish, corrosion, and hydrocarbon deposits that build up on the inside of your diesel tank. The additive is compatible with ULSD, but, more importantly, it can also revitalize the bad fuel that's already in the tank. So you don't need to drain it, you just need to let the product sit for a day or more while it does its work. Organic compounds are broken down, while larger sludge particles get trapped by your fuel filter.

Pros

Cleans contaminated tanks, compatible with ULSD

Cons

Have a few extra fuel filters when you use it, because if it does its job, your filters get clogged

8. Opti-Lube Ag Formula Diesel Fuel Additive

Farm equipment faces different tasks and conditions than on-road diesel engines. Think sitting for months between seasons, operating in extreme temperatures, and getting fuel from diesel storage that's maybe been sitting a bit longer than it should.

Opti-lube AG is designed with those needs in minds. To start, it adds lubricity, something missing from ULSD and necessary for older off-highway diesel engines. That helps everything inside the engine run more smoothly. It also ensures the fuel is safe for longer storage, keeping water and diesel separate in the tank (so your filter can catch the water more easily) while inhibiting bacteria and algae growth. These things are even more important with B5 and B10 diesel fuels. Finally, it boosts the cetane rating by five to seven points for better cold starts and better fuel economy. While it contains some anti-gelling properties, the manufacturer recommends its winter blend for cold seasons.

Pros

Designed for agricultural equipment needs, adds lubricity, helps keep water and diesel separate in the tank

Cons

Not for cold weather use

9. LIQUI MOLY Super Diesel Additive

LIQUI MOLY is well known in Europe, and since Europe has more diesel cars than the U.S., they probably know what they're doing. Super Diesel Additive is made in Germany, designed for all conventional and bio-diesel fuels, and is compatible with turbocharges and diesel particulate filters as well as catalytic converters.

This product removes deposits in the diesel injection system as well as the combustion chamber and stops new deposits from building up. That, the company says, improves ignition performance and leads to lower emissions, less wear, and improved fuel economy. One can is also the ideal size for most light-duty diesel trucks and cars, with a bottle treating 20 gallons of diesel.

The additive also works for decommissioning and preserving engines, with special instructions specific to diesel vehicles you're planning on storing instead of driving right away. The manufacturer says it's ideal for modern high-pressure diesel engines including construction machinery and stationary engines like generators.

Pros

Well tested in a wide range of applications, made in Germany, reputable brand, improves ignition performance and fuel economy

Cons

Paying a price premium for the amount you're getting

10. DPF Remedy

This recommendation is a fuel system cure that says it will reduce the frequency of your modern diesel's regeneration cycles. That's the cycle when your diesel runs extra hot to burn off the soot in your particulate filter that keeps harmful particulates out of the air that comes out of your truck.

These tablets claim to reduce soot in your exhaust by as much as 88 percent thanks to cleaner combustion, and that is good for reducing regenerations as well as your EGR valves and cooler. Reviews for the product said that it reduced regenerations from every 200 miles to more than 1,000 miles, as well as other customers claiming increased range on a tank of fuel. The manufacturer says that lab testing shows the quick dissolve tablets and formula means there are virtually no traces of the organic-metallic compounds used in the fuel burned, which is good for your catalytic converter. The solid tablets are also easier to use than a liquid.

Pros

Cleans DPF filter, tablets are easier to use than liquid, reduces soot from your exhaust

Cons

Not an anti-microbial or anti-gel additive

Why Use Diesel Fuel Additives?

Image credit: nexus 7 / Shutterstock.com

Diesel fuel can be more sensitive than gasoline. While gas tends to slowly lose its most easily combustible components, diesel can more readily absorb water and grow bacteria and algae in the tank. Absorbing water makes it tougher for your fuel filter and water separator to keep up, requiring more frequent service. The proper fuel additive bonds with the water to help it get filtered out more easily. Diesel additives can also stop bacteria and algae from growing in the tank, and that can stop those contaminants from clogging your filters and injectors and damaging expensive fuel pumps. These are all crucial if your diesel-powered vehicle is going to sit for medium to long term periods, or if a tank of fuel lasts you more than a few months.

More importantly, since diesel is often in lower demand than gas, additives can save your engine from the effects of diesel that's been in the fuel station storage tank for too long and suffered the effects of water and algae.

Diesel fuel contains paraffin wax, which slowly crystallizes when it becomes cold. At near and below-freezing temperatures, untreated diesel can turn into a gel, and your fuel system can't pump gel. Diesel fuel additives for winter can stop this gelling, even if you're still using summer-blend fuel. One additive on this list can even restore diesel after it has turned to gel, letting you get on your way.

Lubricity Essential for ULSD

A few years ago, emissions changes led to a big reduction in the amount of sulfur in diesel fuel. In older engines, this sulfur helped to lubricate the top of the cylinders. The cylinder walls, the valves, and any other internal parts that saw contact with fuel, including injector pumps. With ULSD, your engine may not get all of the lubricating it needs in the upper part and fuel system. Most additives fix this, helping your engine to run more smoothly.

Clean Out Harmful Deposits

Lastly, diesel fuel additives can help break down carbon deposits and other deposits in your engine and fuel system. This restores compression and proper injector sprays, letting your engine start quicker and easier, and can restore power and fuel economy.


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Main photo credit: r.classen / Shutterstock.com

Evan Williams
Evan Williams

Evan moved from engineering to automotive journalism 10 years ago (it turns out cars are more interesting than fibreglass pipes), but has been following the auto industry for his entire life. Evan is an award-winning automotive writer and photographer and is the current President of the Automobile Journalists Association of Canada. You'll find him behind his keyboard, behind the wheel, or complaining that tiny sports cars are too small for his XXXL frame.

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 2 comments
  • Gregg Thompson Gregg Thompson on Dec 21, 2022

    Schaeffer Lubricants fuel additives are formulated with 183 years in business. Our additive package outperforms all others and when you perform the cost per treated gallon, especially cold weather concentration, Schaeffer is better and less expensive than all you have mentioned in your article. Example: read the amount of additional additive needed to get to -20 protection. Howes quart says treats 320 gallons but to reach something close to Schaeffers' that quart only treats 80 gallons.Howes would be about 3x more expensive . Call if you want 320-766-0772

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    • Bean Bean Bean Bean on Jan 02, 2023

      @David Traver Adolphus None of these additives are good. FPPF the is the best on market. Should've done some research with this, no other fuel additive regular or diesel compares to it

  • Mario Burgos Mario Burgos on Dec 21, 2022

    Schaeffers products are awesome! Im very satisfied with the Oil, grease and additives.

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