Wash and Decontamination
The Best Engine Bay Cleaner in 2026
An engine bay is aluminum, plastic, rubber and wiring as much as it is grease, so the most useful thing a degreaser maker can publish is what the product will not harm.
By Sawyer V. · Last verified 2026-09-10
We have not tested any of this. Everything below is compiled from published manufacturer specifications, and the arithmetic is printed so you can check it. This page carries affiliate links: if you buy through one we earn a commission at no extra cost to you, and it does not change the order of the picks. Full disclosure.
| # | Pick | Best for | Score | Price |
|---|---|---|---|---|
| 1 | Mothers Professional Water-Based Degreaser Concentrate Mothers | The only degreaser that says it will not harm aluminum | 7.1/10 | Check price on Amazon |
| 2 | Chemical Guys Signature Series Orange Degreaser Chemical Guys | One citrus degreaser for engine, undercarriage and tires | 6.2/10 | Check price on Amazon |
| 3 | Adam's Citrus Degreaser Adam's Polishes | A degreaser stated gentle enough for delicate surfaces | 5.5/10 | Check price on Amazon |
| 4 | Chemical Guys Grime Reaper Engine Degreaser Chemical Guys | A foaming degreaser sold specifically for engines | 5.1/10 | Check price on Amazon |
| 5 | 3D Orange Degreaser 3D Car Care | A water-based citrus degreaser by the gallon | 4.8/10 | Check price on Amazon |
| 6 | 3D Grand Blast Heavy Duty Degreaser 3D Car Care | Nothing here, until the size is published | 4.2/10 | Check price on Amazon |
No live price is currently verified, so every button here reads Check price rather than a number we cannot stand behind. Why we do it that way.
An engine bay is not just grease
The dirt under the hood is oil, road film and baked-on grime, and it sits on cast aluminum, painted metal, plastic covers, rubber hoses and wiring. A degreaser strong enough for the first can be hard on the second, which is why the line that matters most on a degreaser listing is the one about what it will not harm.
Three makers publish one. Mothers state their water-based degreaser will not stain paint or harm aluminum engine components. Adam’s state their Citrus Degreaser is safe on all surfaces, including delicate finishes. 3D state Grand Blast is safe on metals, plastics and rubbers, and then do not say how big the bottle is.
| Degreaser | Sizes | Published chemistry | Surface safety published | Cheapest per oz |
|---|---|---|---|---|
| Mothers Professional Water-Based | 1 gallon / 5 gallons | Surfactants, biodegradable solvents; non-toxic | Will not stain paint or harm aluminum | $0.18 |
| Adam's Citrus Degreaser | 16 oz / gallon | Citrus, Foam Burst lather, corrosion inhibitors | All surfaces, including delicate finishes | $0.43 |
| 3D Orange Degreaser | 16 oz / gallon | Limonene from citrus peel, water-based | Not stated | $0.27 |
| Chemical Guys Signature Series Orange | 16 oz / gallon | Citrus, high-foaming | Not stated | $0.39 |
| Chemical Guys Grime Reaper | 16 oz / gallon | Not published | Not stated | $0.47 |
| 3D Grand Blast | Not published | Water-based, biodegradable | Metals, plastics, rubbers | Unknowable |
Citrus and water-based, and what those words tell you
Four of the six are sold as citrus-based or water-based. 3D explain the distinction they are drawing: limonene oils from citrus peel in a water-based formula, which evaporates more slowly than petroleum solvents and so gives more working time. Chemical Guys and Adam’s describe their degreasers as citrus-based without naming the solvent.
Foam for vertical surfaces
An engine bay is mostly vertical and upside-down surfaces, and liquid runs off them before it works. Adam’s Foam Burst lather is stated to cling and extend working time, and Chemical Guys describe both of theirs as high or intense foaming. Adam’s include a foaming sprayer with the 16 oz bottle only; for your own bottle, the spray bottle roundup covers foaming triggers.
The method the makers publish
Adam’s publish the most complete one: make sure the surfaces are cool, wet them first if you can, spray liberally, allow several minutes of dwell, agitate with a soft-bristled brush and rinse with clean water, repeating for stubborn contamination. None of the six publishes a dilution ratio.
What to buy
- The only published aluminum statement, and the cheapest by the ounce: Mothers Professional, $23.00 a gallon.
- A pint with a foaming sprayer, stated safe on delicate finishes: Adam's Citrus Degreaser, $14.99.
- Water-based citrus by the gallon: 3D Orange Degreaser, $34.99.
- The cheapest pint: Chemical Guys Signature Series Orange, $11.99.
- An engine-specific foam: Chemical Guys Grime Reaper, $13.99.
Every pick, with the working
Each entry lists the specifications the maker publishes, the axis scores those specifications produce, and what you give up. Rows that read “Not published” are not omissions on our side: they are figures the maker will not commit to in writing, and they cost the product points on the transparency axis.
Our pickThe only degreaser that says it will not harm aluminum
Mothers Professional Water-Based Degreaser Concentrate
Mothers
$23.00 a gallon of a non-toxic super-concentrate with grease-cutting surfactants and biodegradable solvents, and Mothers state the two things an engine bay needs to hear: it will not stain paint or harm aluminum engine components.
- Sizes
- 1 gallon ($23.00), 5 gallon ($114.72)
- Chemistry
- Grease-cutting surfactants, biodegradable solvents; non-toxic
- Surface safety
- Will not stain paint or harm aluminum engine components
- Dilution ratio
- Not published
What it does well
- Will not stain paint or harm aluminum, stated
- Biodegradable solvents and non-toxic, stated
- $23.00 a gallon is 18 cents an ounce before dilution
Who it is not for
- Sold by the gallon or 5 gallons only
- No dilution ratio published
- No dwell time published
How this score was calculated
- Protection claimdropped
- Nothing in this category is bought on how long it lasts, so the axis is dropped and the other weights are re-normalized.
- Capabilitydropped
- No single published number decides capability in this category, so the axis is dropped rather than invented.
- Cost per ounce10.0/10, weight 16%
- $23.00 for 128 oz works out at $0.18 an ounce, scored against a band of $0.20 (good) to $1.20 (expensive) for a degreaser.
- Price against the ceiling3.4/10, weight 14%
- A listed $23.00 against the $35 one upgrade in this category realistically tops out at. A list price captured on the compile date, not a live price and not what you will pay.
- Written commitmentdropped
- Mothers publishes no warranty term on this product's own page, so the axis is dropped. On a tool that is worth noticing, and it costs the product points on transparency instead.
- Spec transparency7.5/10, weight 18%
- 3 of the 4 specifications we went looking for are published by Mothers. Every blank row below is something the maker will not put in writing, and it costs the product points here.
List price $23.00 per Mothers' own store, captured on the compile date below. Not a live price and not what you will pay — the button is where the real number is.
Specifications from Mothers Professional Water-Based Degreaser product page, compiled September 8, 2026.
2One citrus degreaser for engine, undercarriage and tires
Chemical Guys Signature Series Orange Degreaser
Chemical Guys
$11.99 for 16 oz or $49.99 a gallon, citrus-based and high-foaming, with dilution options for heavy and light jobs across engines, undercarriages, tools and tires.
- Sizes
- 16 oz ($11.99), 1 gallon ($49.99)
- Chemistry
- Citrus-based, high-foaming
- Stated uses
- Engines, undercarriages, tools, tires
- Surface safety
- Not published
What it does well
- Citrus-based, stated
- Rated for engines, undercarriages, tools and tires
- $11.99 is the cheapest pint here
Who it is not for
- Dilution options mentioned, not given as ratios
- No surface-safety statement for aluminum
- No pH published
How this score was calculated
- Protection claimdropped
- Nothing in this category is bought on how long it lasts, so the axis is dropped and the other weights are re-normalized.
- Capabilitydropped
- No single published number decides capability in this category, so the axis is dropped rather than invented.
- Cost per ounce4.5/10, weight 16%
- $11.99 for 16 oz works out at $0.75 an ounce, scored against a band of $0.20 (good) to $1.20 (expensive) for a degreaser.
- Price against the ceiling6.6/10, weight 14%
- A listed $11.99 against the $35 one upgrade in this category realistically tops out at. A list price captured on the compile date, not a live price and not what you will pay.
- Written commitmentdropped
- Chemical Guys publishes no warranty term on this product's own page, so the axis is dropped. On a tool that is worth noticing, and it costs the product points on transparency instead.
- Spec transparency7.5/10, weight 18%
- 3 of the 4 specifications we went looking for are published by Chemical Guys. Every blank row below is something the maker will not put in writing, and it costs the product points here.
List price $11.99 per Chemical Guys' own store, captured on the compile date below. Not a live price and not what you will pay — the button is where the real number is.
Specifications from Chemical Guys Signature Series Orange Degreaser product page, compiled September 8, 2026.
3A degreaser stated gentle enough for delicate surfaces
Adam's Citrus Degreaser
Adam's Polishes
$14.99 for 16 oz or $54.99 a gallon, an all-purpose cleaner and citrus degreaser with Adam's Foam Burst lather that clings and extends working time, stated safe on all surfaces including delicate ones.
- Sizes
- 16 oz ($14.99), gallon ($54.99)
- Chemistry
- Citrus-based, Foam Burst lather, corrosion inhibitors
- Sprayer
- Foaming sprayer included on the 16 oz only
- Stated surfaces
- All surfaces including delicate ones
- pH
- Not published
What it does well
- Foam Burst lather for cling and working time, stated
- Safe on all surfaces including delicate ones, stated
- Corrosion inhibitors named
- Doubles as an all-purpose cleaner
Who it is not for
- Gallon at $54.99 is 43 cents an ounce
- "All surfaces" is a broad claim
- No pH published
How this score was calculated
- Protection claimdropped
- Nothing in this category is bought on how long it lasts, so the axis is dropped and the other weights are re-normalized.
- Capabilitydropped
- No single published number decides capability in this category, so the axis is dropped rather than invented.
- Cost per ounce2.6/10, weight 16%
- $14.99 for 16 oz works out at $0.94 an ounce, scored against a band of $0.20 (good) to $1.20 (expensive) for a degreaser.
- Price against the ceiling5.7/10, weight 14%
- A listed $14.99 against the $35 one upgrade in this category realistically tops out at. A list price captured on the compile date, not a live price and not what you will pay.
- Written commitmentdropped
- Adam's Polishes publishes no warranty term on this product's own page, so the axis is dropped. On a tool that is worth noticing, and it costs the product points on transparency instead.
- Spec transparency8.0/10, weight 18%
- 4 of the 5 specifications we went looking for are published by Adam's Polishes. Every blank row below is something the maker will not put in writing, and it costs the product points here.
List price $14.99 per Adam's Polishes' own store, captured on the compile date below. Not a live price and not what you will pay — the button is where the real number is.
Specifications from Adam's Citrus Degreaser product page, compiled September 8, 2026.
4A foaming degreaser sold specifically for engines
Chemical Guys Grime Reaper Engine Degreaser
Chemical Guys
$13.99 for 16 oz or $59.99 a gallon, sold as professional strength with intense foaming for engines and engine bays. The listing names the soils - grease, oil, dirt, tar and baked-on grime - and not the chemistry.
- Sizes
- 16 oz ($13.99), 1 gallon ($59.99)
- Stated soils
- Grease, oil, dirt, tar, baked-on grime
- Foam
- Intense foaming
- Chemistry
- Not published
- Surface safety
- Not published
What it does well
- Engine-bay specific, with the soil list published
- Foaming, so it clings to vertical surfaces
- $13.99 pint to try
Who it is not for
- No chemistry named
- No surface-safety statement for aluminum or plastics
- Gallon at $59.99 is the dearest per ounce here
How this score was calculated
- Protection claimdropped
- Nothing in this category is bought on how long it lasts, so the axis is dropped and the other weights are re-normalized.
- Capabilitydropped
- No single published number decides capability in this category, so the axis is dropped rather than invented.
- Cost per ounce3.3/10, weight 16%
- $13.99 for 16 oz works out at $0.87 an ounce, scored against a band of $0.20 (good) to $1.20 (expensive) for a degreaser.
- Price against the ceiling6.0/10, weight 14%
- A listed $13.99 against the $35 one upgrade in this category realistically tops out at. A list price captured on the compile date, not a live price and not what you will pay.
- Written commitmentdropped
- Chemical Guys publishes no warranty term on this product's own page, so the axis is dropped. On a tool that is worth noticing, and it costs the product points on transparency instead.
- Spec transparency6.0/10, weight 18%
- 3 of the 5 specifications we went looking for are published by Chemical Guys. Every blank row below is something the maker will not put in writing, and it costs the product points here.
List price $13.99 per Chemical Guys' own store, captured on the compile date below. Not a live price and not what you will pay — the button is where the real number is.
Specifications from Chemical Guys Grime Reaper product page, compiled September 8, 2026.
5A water-based citrus degreaser by the gallon
3D Orange Degreaser
3D Car Care
$16.99 for 16 oz or $34.99 a gallon - 27 cents an ounce - built on limonene oils from citrus peel in a water-based formula, which 3D contrast directly with petroleum solvents.
- Sizes
- 16 oz ($16.99), 1 gallon ($34.99)
- Chemistry
- Limonene oils from citrus peel; water-based
- Stated targets
- Oily films, traffic film, grease, grime
- pH
- Not published
What it does well
- Limonene chemistry named
- Water-based, stated
- Gallon at $34.99 is 27 cents an ounce
Who it is not for
- No surface-safety statement for engine components
- No pH published
- The pint is poor value against the gallon
How this score was calculated
- Protection claimdropped
- Nothing in this category is bought on how long it lasts, so the axis is dropped and the other weights are re-normalized.
- Capabilitydropped
- No single published number decides capability in this category, so the axis is dropped rather than invented.
- Cost per ounce1.4/10, weight 16%
- $16.99 for 16 oz works out at $1.06 an ounce, scored against a band of $0.20 (good) to $1.20 (expensive) for a degreaser.
- Price against the ceiling5.1/10, weight 14%
- A listed $16.99 against the $35 one upgrade in this category realistically tops out at. A list price captured on the compile date, not a live price and not what you will pay.
- Written commitmentdropped
- 3D Car Care publishes no warranty term on this product's own page, so the axis is dropped. On a tool that is worth noticing, and it costs the product points on transparency instead.
- Spec transparency7.5/10, weight 18%
- 3 of the 4 specifications we went looking for are published by 3D Car Care. Every blank row below is something the maker will not put in writing, and it costs the product points here.
List price $16.99 per 3D Car Care's own store, captured on the compile date below. Not a live price and not what you will pay — the button is where the real number is.
Specifications from 3D Car Care's Orange Degreaser product page, compiled September 8, 2026.
6Nothing here, until the size is published
3D Grand Blast Heavy Duty Degreaser
3D Car Care
Skip this one. $34.99 with no bottle size anywhere on the listing, so there is no way to compare it with anything else here. 3D's own Orange Degreaser publishes its size and costs 27 cents an ounce by the gallon.
$34.99 for a water-based, biodegradable engine degreaser 3D state is safe on metals, plastics and rubbers. The bottle size is not stated anywhere on the listing.
- Stated use
- Engine degreasing
- Materials
- Stated safe on metals, plastics and rubbers
- Chemistry
- Water-based, biodegradable
- Size
- Not published
What it does well
- Stated safe on metals, plastics and rubbers
- Water-based and biodegradable, stated
Who it is not for
- No size published, so cost per ounce is unknowable
- $34.99 is the highest single price here
- No dilution or dwell time published
How this score was calculated
- Protection claimdropped
- Nothing in this category is bought on how long it lasts, so the axis is dropped and the other weights are re-normalized.
- Capabilitydropped
- No single published number decides capability in this category, so the axis is dropped rather than invented.
- Cost per ouncedropped
- Either the list price or the container size is unpublished, so the division cannot be done and the axis is dropped.
- Price against the ceiling0.0/10, weight 14%
- A listed $34.99 against the $35 one upgrade in this category realistically tops out at. A list price captured on the compile date, not a live price and not what you will pay.
- Written commitmentdropped
- 3D Car Care publishes no warranty term on this product's own page, so the axis is dropped. On a tool that is worth noticing, and it costs the product points on transparency instead.
- Spec transparency7.5/10, weight 18%
- 3 of the 4 specifications we went looking for are published by 3D Car Care. Every blank row below is something the maker will not put in writing, and it costs the product points here.
List price $34.99 per 3D Car Care's own store, captured on the compile date below. Not a live price and not what you will pay — the button is where the real number is.
Specifications from 3D Car Care's Grand Blast product page, compiled September 8, 2026.
No live price is currently verified, so every button here reads Check price rather than a number we cannot stand behind. Why we do it that way.
Questions people actually ask
+Can I use an all-purpose cleaner on my engine?
+Will degreaser damage aluminum?
+Should the engine be hot or cold when I degrease it?
+What should I put on the engine bay afterwards?
Where these figures came from
- Mothers Professional Water-Based Degreaser product page — retrieved 2026-09-10
- Adam's Citrus Degreaser product page — retrieved 2026-09-10
- 3D Car Care's Orange Degreaser product page — retrieved 2026-09-10
- Chemical Guys Signature Series Orange Degreaser product page — retrieved 2026-09-10
- Chemical Guys Grime Reaper product page — retrieved 2026-09-10
- 3D Car Care's Grand Blast product page — retrieved 2026-09-10
Every figure on this page is a published manufacturer or authorized-retailer claim, not a measurement we made. How we research explains exactly what we did and did not do.