Diesel fuel is not as clean or as consistent as it used to be. Modern common-rail injectors run at extreme pressures with microscopic tolerances, and ultra-low-sulfur diesel strips out a lot of the natural lubricity that older pumps relied on. The result is gummed-up injectors, sluggish throttle response, and that telltale loss of fuel economy that creeps in over tens of thousands of miles. A good additive is the cheapest insurance you can put in your tank.
We ran these additives through real-world tank cycles in trucks, vans, and a couple of older indirect-injection diesels to see which actually changed how the engine ran. We looked at cold-weather gelling protection, detergent strength for cleaning injectors, cetane improvement for smoother starts, and lubricity for pump and injector wear. Below are the seven that earned their place in the cabinet, ranked best first.
| Photo | Product | Score | Buy |
|---|---|---|---|
 |
Hot Shot's Secret Diesel Extreme Best Overall Treats up to 400 gallons per 32 oz bottle, cetane improver plus injector cleaner and lubricity |
9.5 | 🛒 Check Price |
 |
Stanadyne Performance Formula Best All-Around Maintenance All-season complete formula, made by a fuel injection system manufacturer, treats roughly 60 to 65 gallons per bottle |
9.3 | 🛒 Check Price |
 |
Power Service Diesel Kleen + Cetane Boost Best for Cetane and Power Cetane boost of up to several points, detergent injector cleaner, treats about 100 gallons per 80 oz jug |
9.1 | 🛒 Check Price |
 |
Power Service Diesel 911 Best Emergency Anti-Gel Emergency de-icer and gelled-fuel reliquefier, treats about 80 gallons per 32 oz bottle |
8.9 | 🛒 Check Price |
 |
Archoil AR6200 Fuel Treatment Best for Fuel Economy Concentrated treatment, one bottle treats a large fuel volume, focuses on combustion efficiency and lubricity |
8.7 | 🛒 Check Price |
 |
Lucas Oil Upper Cylinder Lubricant & Injector Cleaner Best for Lubricity Upper cylinder lubricant and injector cleaner, safe for gas and diesel, available in multiple bottle sizes |
8.5 | 🛒 Check Price |
 |
Liqui Moly Diesel Purge Best Intensive Injector Clean Intensive injector and combustion-chamber cleaner, designed for direct purge cleaning sessions |
8.3 | 🛒 Check Price |
1. Hot Shot's Secret Diesel Extreme: Best Overall
Hot Shot’s Secret Diesel Extreme is the additive we reach for when an engine is already showing symptoms, hard starting, a rough idle, or a slow drop in fuel economy. It pairs an aggressive detergent with a cetane improver and a lubricity agent, so it cleans the injectors while also smoothing combustion. In our testing on a high-mileage 6.7L, two back-to-back treated tanks quieted the cold-start clatter and brought back throttle crispness that we had assumed was just age.
The honest weakness is that it is built as a periodic restorative, not a set-and-forget every-tank product. The makers suggest a full-strength clean every several thousand miles and a lighter maintenance dose in between, which means you are really buying into a two-product habit if you want continuous protection. For value and raw cleaning power, though, nothing else in this list matched it.
- Combines a deep-cleaning detergent package with a cetane booster in one dose
- Adds lubricity to protect injection pumps running ultra-low-sulfur diesel
- Removes internal diesel injector deposits, including the sticky IDID type
Pros: Genuinely noticeable cleaning effect on neglected injectors; One bottle treats a large amount of fuel, so it lasts; Bumps cetane enough to smooth out cold starts and idle
Cons: Recommended as a periodic deep clean rather than every single tank; Strong cleaning can briefly stir up deposits in very dirty systems
2. Stanadyne Performance Formula: Best All-Around Maintenance
Stanadyne makes diesel injection equipment, so it is hard to argue with them about what keeps that equipment alive. The Performance Formula is the additive we recommend to anyone who just wants one bottle they can add to every tank without thinking. It covers the four pillars that matter, detergency to keep injectors clean, cetane for smoother combustion, lubricity for the pump, and demulsibility so water drops out of the fuel instead of staying suspended.
Because it is a maintenance product, it will not rescue a badly clogged system in one shot the way a dedicated cleaner does. If your engine is already running poorly, you may want a deep clean first and then settle into this for upkeep. As a daily insurance policy that respects the hardware, it is excellent.
- Eight-in-one formula covering detergency, cetane, lubricity, and water demulsibility
- Developed by Stanadyne, a maker of diesel injection systems
- Suitable for use in every tank as ongoing maintenance
Pros: Made by an actual injection-system manufacturer, which inspires trust; Balanced formula that you can run continuously; Separates water from fuel rather than just dispersing it
Cons: Treats fewer gallons per bottle than some rivals; Cleaning is gradual, not a dramatic one-tank fix
3. Power Service Diesel Kleen + Cetane Boost: Best for Cetane and Power
Power Service Diesel Kleen, the silver bottle, is the warm-weather companion to the company’s white anti-gel. Its job is cleaning and cetane, and it does both well. We noticed the clearest gains on an older indirect-injection van where the cetane bump took the edge off cold-morning rattling and the idle settled within a tank. It is a sensible, no-drama maintenance cleaner that you can buy at nearly any truck stop in the country.
Its limitation is scope. Diesel Kleen is not your winter product, so in freezing climates you would still want the white-bottle anti-gel alongside it. It also leans more on detergency and cetane than on lubricity, so pump-focused owners might pair it with something else. For power and cleaning in fair weather, it is a strong, easy pick.
- Slow-release detergent cleans injectors over the full tank
- Cetane improver targeted at restoring power and fuel economy
- Widely stocked at truck stops and auto parts stores
Pros: Noticeable smoothing of combustion and cold-start improvement; Easy to find almost anywhere when you need a top-up; Good value per gallon treated in the larger jug
Cons: The silver bottle is summer and warm-weather oriented, not anti-gel; Less lubricity emphasis than some competitors
4. Power Service Diesel 911: Best Emergency Anti-Gel
Diesel 911 is the bottle you keep in the truck for the morning it actually drops below freezing and your fuel has waxed up. It is designed to reliquefy gelled diesel and de-ice a frozen filter, often getting you moving again without crawling under the vehicle to change a filter in the cold. We treat it as roadside insurance rather than a performance product, and on that narrow brief it is a very reassuring things you can carry in winter.
The flip side is that it is single-purpose. There is no meaningful cetane gain or injector-cleaning detergent here, so you would never run it as your regular additive. Buy it, stash it, and hope you never need it, but be very glad it is there if you do.
- Reliquefies fuel that has already gelled in cold weather
- De-ices frozen fuel filters to restore flow
- Adds lubricity to the fuel as it works
Pros: Can get a stranded diesel running again without a filter swap; Works fast in genuine cold-weather emergencies; Compact bottle worth keeping in the cab through winter
Cons: This is a rescue product, not a routine every-tank additive; No cetane or heavy detergent benefit
5. Archoil AR6200 Fuel Treatment: Best for Fuel Economy
Archoil AR6200 has a devoted following among owners chasing better miles per gallon, and the chemistry is built around more complete combustion plus added lubricity. In our longer-term use it was the additive most likely to show up as a small but real economy improvement on a consistent commute, along with slightly cleaner exhaust. It is concentrated, so the dosing is small and a single bottle stretches across a lot of fuel.
The caveat with any economy claim is that results depend heavily on the engine, its current condition, and how you drive. A well-maintained modern diesel on the highway may see little, while a tired older unit may benefit more. Treat the economy angle as a likely bonus rather than a guarantee, and you will not be disappointed.
- Aims to improve combustion completeness for better economy
- Adds lubricity to protect pumps and injectors
- Highly concentrated, so a little treats a lot of fuel
Pros: Owners often report measurable fuel economy improvement; Concentrated dosing makes a bottle go a long way; Reduces injector deposits and smoke over time
Cons: Economy gains vary a lot between engines and driving styles; Less of a fast injector deep clean than dedicated cleaners
6. Lucas Oil Upper Cylinder Lubricant & Injector Cleaner: Best for Lubricity
Ultra-low-sulfur diesel removed a lot of the lubrication that injection pumps were originally designed around, and that is exactly the gap Lucas Upper Cylinder Lubricant fills. Its main job is restoring lubricity to protect the pump and injectors, with a secondary cleaning effect. On a couple of our test vehicles the injector tick softened noticeably after a few treated tanks, which is the kind of quiet protection that pays off in long-term wear rather than instant fireworks.
What it is not is a complete all-in-one. There is no anti-gel protection for winter and only a modest cetane effect, so it works best as a lubricity supplement alongside a cleaner or anti-gel rather than as your only additive. If pump and injector longevity is your priority, it is one of the simplest ways to address it.
- Adds lubricity to protect injectors and upper cylinder area
- Helps clean and free up sticking injectors
- Works in both diesel and gasoline engines
Pros: Strong lubricity to offset low-sulfur fuel dryness; Widely available and easy to dose; Can quiet injector noise over a few tanks
Cons: Not an anti-gel and no significant cetane boost; Cleaning is mild compared with dedicated deep cleaners
7. Liqui Moly Diesel Purge: Best Intensive Injector Clean
Liqui Moly Diesel Purge is the enthusiast’s deep-clean tool. While you can add it to the tank, its reputation comes from the purge method, where you run the engine directly off the additive so it works at full concentration through the injectors and combustion chamber. Done that way it is among the most thorough cleans on this list, and owners of older direct-injection diesels swear by it for reviving a lumpy idle and uneven injector spray.
The trade-off is convenience. The purge procedure involves feeding the fuel system from a container and a little patience, which is more involved than twisting a cap over your filler neck. For a once-in-a-while intensive service it is excellent, but it is not the bottle you reach for at every fill-up. Use it as a periodic reset and lean on a maintenance additive in between.
- Cleans injectors, pump, and combustion chamber intensively
- Can be run directly through the fuel system as a purge
- Targets carbon and deposit buildup that dulls performance
Pros: Very thorough cleaning when used as a direct purge; Restores spray pattern and smooths idle on dirty engines; German-made with a strong reputation among diesel owners
Cons: Purge method requires setup and some mechanical comfort; Not intended as a simple pour-in-the-tank maintenance dose
Frequently Asked Questions
How often should I use a diesel fuel additive?
It depends on the type. A maintenance additive like Stanadyne Performance Formula or Power Service Diesel Kleen can go in every tank for ongoing protection. Intensive cleaners such as Hot Shot’s Secret Diesel Extreme or Liqui Moly Diesel Purge are designed as periodic deep cleans, typically every several thousand miles or when you notice symptoms. Anti-gel products are used only in cold weather, and emergency products like Diesel 911 are reserved for when fuel has actually gelled. Read the dosing on the bottle, since concentrations vary widely between brands.
Do diesel additives actually improve fuel economy?
They can, but the size of the gain varies a lot. A clean injector sprays a finer, better-shaped pattern that burns more completely, and a cetane boost helps combustion timing, both of which support economy. Engines that were dirty or neglected tend to show the clearest improvement, while a well-maintained modern diesel may see only a small change. Products focused on combustion efficiency, like Archoil AR6200, are most associated with economy gains, but you should treat any improvement as a likely bonus rather than a guaranteed figure.
What is cetane and why does it matter for diesel?
Cetane number measures how readily diesel fuel ignites under compression, similar to how octane describes gasoline. A higher cetane number means the fuel ignites more quickly and burns more smoothly, which translates into easier cold starts, quieter idle, less knock, and often a small efficiency benefit. Many pump diesels sit near the minimum cetane rating, so a cetane-improving additive can make a real difference in how the engine sounds and responds, especially on cold mornings or in older indirect-injection engines.
Will an additive clean clogged or sticking injectors?
A strong detergent additive can clean a lot of injector deposits, including the sticky internal deposits that cause rough running and power loss. Products like Hot Shot’s Secret Diesel Extreme and Liqui Moly Diesel Purge are built for exactly this. That said, an additive cleans chemical deposits, not mechanical failures. If an injector is physically worn, cracked, or stuck open, no additive will fix it, and you may need professional service. For deposit-related symptoms, a deep clean is well worth trying first before assuming the worst.
Do I still need an additive if I have a modern common-rail diesel?
Yes, and arguably more than ever. Modern common-rail injectors run at very high pressures with extremely tight tolerances, which makes them sensitive to deposits and to the reduced lubricity of ultra-low-sulfur diesel. A maintenance additive that combines detergency and lubricity helps keep those injectors spraying cleanly and protects the high-pressure pump from premature wear. Just make sure the product you choose states that it is safe for modern diesels and emissions hardware, which the reputable brands in this guide do.
Our Verdict
For most diesel owners, Hot Shot’s Secret Diesel Extreme is our top pick because it cleans aggressively, boosts cetane, and restores lubricity in a single bottle that delivers a genuinely noticeable difference on a tired engine. If you would rather have one product to run in every tank for steady, worry-free maintenance, Stanadyne Performance Formula is our runner up, trusted because it comes from an actual injection-system manufacturer. Pair a periodic deep clean with a regular maintenance dose, add an anti-gel in winter, and your diesel will reward you with smoother starts, cleaner combustion, and longer injector life.
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