Best Engine Cleaning Additive (2026): 4 Picks Compared
Four engine cleaning additives for diesel and small gas engines, compared by what they clean, treat size, use and warranty.
On this page
Top picks at a glance
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- 1
Best OverallHot Shot’s Diesel9.7/10View on Amazon - 2
Best Small EngineSTA-BIL Small Engine9.6/10View on Amazon - 3
Also ConsiderLiqui Moly Cera Tec9.5/10View on Amazon
An engine that idles rough and feels down on power often has deposits in the fuel system. Gum and varnish build up in small engines, and injectors lose their spray pattern as deposits form. The best engine cleaning additive clears gum, varnish and injector deposits so the engine runs the way it should.
This guide compares the best engine cleaning additive options by what they clean, the engines they fit, treat size and warranty, using only what each listing states.
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Quick picks
- Best Overall Hot Shot’s Diesel: 32 oz treats 80 gallons, cleans injector deposits and raises cetane, with a 1 year limited warranty. Check price on Amazon
- Best Small Engine STA-BIL Small Engine: 16 fl oz for gas-powered small engines, cleans gum and varnish and protects against ethanol. Check price on Amazon
- Also Consider Liqui Moly Cera Tec: 300 ml ceramic wear protection for petrol and diesel engines, per the title. Check price on Amazon
Picks for the garage
Hot Shot's Secret Diesel Extreme 32 oz
A 32 oz diesel fuel additive that treats 80 gallons, cleaning injectors and raising cetane, with a 1 year limited warranty.
Pros
- Treats 80 gallons from a 32 oz bottle
- Flushes injector deposits, water and sludge
- Raises cetane for faster starts and smoother idling
- 1 year limited warranty
Cons
- Bullets and spec table give different bottle dimensions and weights
- Diesel only, not for gas engines
- No safety certification is stated
- Only the 32 oz size is listed
STA-BIL Small Engine Pro Multi-System Additive
A 16 fl oz additive for small gas engines that cleans gum and varnish, lubricates parts and protects against ethanol.
Pros
- Cleans gum and varnish to restore lost power
- Lubricates valves and pistons
- Protects against ethanol with corrosion inhibitors
- Made for lawn mowers, trimmers, chainsaws, generators and more
Cons
- No warranty term is stated, only a satisfaction guarantee
- No safety certification is stated
- No treat size is stated
- Gas small engines only, not diesel
LIQUI MOLY Oil Additive Cera Tec 20002 Ceramic
A ceramic wear protection additive for petrol and diesel engines, mixable with all commercially available motor oils, with claims around smoother performance, less friction and lower fuel consumption.
Pros
- Ceramic wear and tear protection for petrol and diesel engines
- Mixable with all commercially available motor oils
- Stable under high thermal and dynamic permanent loads
- No deposits, compatible with commonly used filter systems
Cons
- No warranty term is stated in the listing
- No safety listing is stated in the listing
- No mixing ratio is stated in the listing
- Performance claims are maker claims, not measured results
Safe & Effective - Engine Oil Additive/Treatment
A 12oz diamond nano-lube engine oil treatment for gas, diesel, hybrid and racing engines, with cleaning detergents and protective additives.
Pros
- Maker claims friction reduced by up to 60 percent
- Stated heat resistance up to 1,800 degrees Fahrenheit (982 degrees Celsius)
- Cleaning detergents plus protective additives, per the listing
- Clear dose: one bottle for every 5 quarts of oil
Cons
- No warranty term is stated
- Friction and heat figures are maker claims, not stated results
- No weight is stated in the listing
- No flash point is stated
Compared on paper
| Model | Shop Score | Type | Treats | Engines | Warranty |
|---|---|---|---|---|---|
| Hot Shot’s Diesel | 9.7/10 | Diesel fuel additive | 80 gallons | Diesel | 1 year limited |
| STA-BIL Small Engine | 9.6/10 | Gasoline/oil additive | Not stated | Gas small engines | Not stated |
| Liqui Moly Cera Tec | 9.5/10 | Oil additive | Not stated | Petrol and diesel | Not stated |
| BestLine Nano-Lube | 9.4/10 | Oil additive | Not stated | Gas and diesel | Not stated |
Specifications are manufacturer rated, as published on each listing and collected 1 November 2026. Where a listing contradicts itself, both figures are shown.
How the points were given
Each additive is scored on performance, build, value, safety and warranty, with the weights published on the How We Pick page. None of the listings states a safety certification, and only 1 states a warranty term, so 3 score zero on warranty and all 4 score zero on safety.
| Product | Shop Score | Perf. /35 | Build /25 | Value /25 | Safety /10 | Warranty /5 |
|---|---|---|---|---|---|---|
| Hot Shot’s Diesel | 9.7 | 30 | 21 | 20 | n/a | 2 |
| STA-BIL Small Engine | 9.6 | 29 | 21 | 20 | n/a | 0 |
Scores run from 9.2 to 9.8: each product’s point total is placed on that range, so more points always means a higher score. Safety counts only for powered gear or where the listing states safety features; where it does not apply, the score is taken over the remaining 90 points.
What the listings tell you
4 additive listings were compared. Two give a full set of bullets and a spec table, and 2 give a title only. One states a warranty term, and none states a safety certification. One states a treat size of 80 gallons, and 1 gives a size of 300 ml with no treat size. One listing gives its bottle dimensions 2 ways.
Buying guide: the best engine cleaning additive for your garage
Diesel or gas
The Hot Shot’s is made for diesel engines, and the STA-BIL is made for gas-powered small engines. The Cera Tec lists petrol and diesel engines, and the Nano-Lube lists gas and diesel engines. Match the additive to the fuel your engine burns, because the diesel additive never mentions gas engines and the small engine additive never mentions diesel.
Fuel additive or oil additive
The Hot Shot’s is a fuel additive and fuel system cleaner that goes in the fuel. The STA-BIL is a gasoline and oil additive for small engines. The Cera Tec and the Nano-Lube are oil additives and treatments. The listing tells you which system each one is made for, so read it before buying.
Treat size
Only the Hot Shot’s states a treat size: a 32 oz bottle treats 80 gallons. The STA-BIL states a 16 fl oz bottle with no treat size, the Cera Tec states 300 ml with no treat size, and the Nano-Lube states no size at all. Without a treat size, the listing gives no way to judge how far a bottle goes.
Warranty
Only the Hot Shot’s states a warranty term: 1 year limited. The STA-BIL states a 100% satisfaction guarantee with no term in years or months, so no warranty term can be read from it. The Cera Tec and the Nano-Lube state no warranty at all.
What the title-only listings leave out
The Cera Tec and the Nano-Lube give a title only, with no bullets and no spec table. That leaves out dilution, treat size, warranty and any safety statement. Check the title for the size: the Cera Tec states 300 ml, and the Nano-Lube states no size at all.
Use rated jack stands on solid ground, wear eye protection with power and air tools, keep fuel-burning equipment out of a closed garage, and follow the manual for every tool. Read our Safety Disclaimer.
Garage Fit Check
- Check the engine first: the Hot Shot’s is for diesel, the STA-BIL is for gas-powered small engines, and the other 2 list gas and diesel.
- Check the treat size: only the Hot Shot’s states one, at 80 gallons per 32 oz bottle.
- Check the bottle size: 32 oz for the Hot Shot’s, 16 fl oz for the STA-BIL, 300 ml for the Cera Tec, and no size stated for the Nano-Lube.
- Check the warranty wording: 1 states 1 year limited, 1 states a satisfaction guarantee with no term, and 2 state no warranty.
FAQ: garage tools
What are engine oil additives?
Additives are liquids added to fuel or oil that clean or protect the engine. The Hot Shot’s flushes injector deposits from the fuel system, the STA-BIL cleans gum and varnish in small engines, and the Cera Tec and Nano-Lube describe friction and wear protection in the oil.
What is the best engine additive?
It depends on the engine. The Hot Shot’s is made for diesel fuel systems, the STA-BIL for small gas engines, and the Cera Tec and Nano-Lube list both petrol and diesel engines. Pick the one that names your engine and fuel.
Can I use a diesel additive in a gas engine?
Not according to these listings. The Hot Shot’s is a diesel fuel additive and never mentions gas engines, while the STA-BIL is made for gas-powered small engines and never mentions diesel. The Cera Tec and Nano-Lube are the only 2 here that list both.
What does cetane mean for a diesel additive?
The Hot Shot’s listing says raising cetane gives faster starts, smoother idling and stronger acceleration in diesel engines. The other listings do not mention cetane.
Do any of these additives have a warranty?
Only the Hot Shot’s states a warranty term: 1 year limited. The STA-BIL states a satisfaction guarantee with no term, and the Cera Tec and Nano-Lube state no warranty.
Related: the best engine oil additive, the best diesel fuel additive, the best oil additive for diesel and the best engine oil additive for high mileage. Also see our engine and shop equipment hub.
