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Working under the hood of your car can be satisfying and even fun. It can also save you a lot of money.

There are some tasks that might not seem worth the effort or the mess, though. And degreasing the engine would be at the top of many peoples’ list – unless they were about to sell their car and wanted it to look as clean as the day it was purchased.

That approach is a little short-sighted. There are good reasons to degrease your engine, and they have nothing to do with the myth that accumulated oil and dirt can cause an engine to overheat. That almost never happens.

But degreasing every so often can end up saving you big money on other repairs, primarily because you’ll be able to see small issues like broken hose connections and oil leaks before they become expensive problems. Removing the gunk will also prevent excess wear on hoses and other parts, so they’ll last longer.

If nothing else, it’ll make the work space cleaner for the next time you have to get under the hood.

Best Overall
Gunk
15 oz
Best Value
Meguiar’s
128 fl. oz.
Best on a Budget
Zep
13 oz

The Engine Degreasers

1. Gunk Engine Degreaser

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Gunk is a petroleum-based solvent, manufactured by a family-owned business in North Carolina, and professional mechanics and dedicated DIYers swear by it. That’s because it’s extremely powerful, able to cut through the toughest baked-on engine grease and grime with a single application. (It’s so strong that it’s illegal for sale in California.)

This degreaser works quickly and easily; you simply spray it onto your engine (make sure not to get it on electronics or painted plastic parts), let it sit for 15 minutes, and hose it off, with no need for hand drying unless you’ve inadvertently gotten into somewhere it doesn’t belong. You’ll be amazed at how clean your engine will be.

The petroleum base means that Gunk smells terrible, so you’ll definitely want to use a mask when using it (or avoid using it completely if you’re medically sensitive to the odor). There’s a separate Gunk engine shine product, CEB1, which you can apply afterward if desired; it will help prevent engine buildup, so you won’t have to degrease as frequently. This is the gold standard.


2. Chemical Guys Signature Series Degreaser

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Here’s the good news for those on a budget: you can buy a single spray container of this citrus-based degreaser. And here’s the good news for those who are environmentally conscious: there are no toxic ingredients in the Chemical Guys degreasing formula. It uses organic cleaning ingredients to loosen and emulsify built-in engine grease, grime and other gunk.

This is a concentrate, which can be diluted to your desired strength according to the ratio chart included with the product. At a 6:1 high strength concentration it’s great for degreasing messy engines which haven’t been touched for a while. But it’s also a multi-purpose product when substantially diluted at 15:1 or even 40:1, when it can be used to clean tires, tools or dirty areas of your garage or shop. It also works well to clean RVs, bikes and off-road vehicles covered in mud and road grime.

The degreaser is simple to use; you simply spray it on, let it sit for one minute, and then wash it off. Even though the Chemical Guys product is non-toxic it’s quite strong, so gloves and face masks should be the order of the day. It won’t do as much damage as petroleum-based degreasers if accidentally splashed onto non-engine parts under the hood, but avoid getting it onto paint – and as with all degreasers, it’s not recommended for cleaning brake parts.

For a product that isn’t petroleum-based, this is an impressive degreaser. While it doesn’t smell pleasant, it doesn’t smell as bad, either.


3. Meguiar’s Super Degreaser

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There are no petroleum distillates in this Meguiar’s degreaser, but it does contain caustic chemicals like potassium hydroxide, so use it with caution and protection, and wash it off as quickly as possible because it can etch right through aluminum. When you do use it, though, it will make quick work of grease and grime that builds up on vehicle engines without depositing the telltale white residue that’s left behind by some lesser products.

The Meguiar’s degreaser isn’t cheap, but since it’s a concentrate you can get plenty of use out a single bottle. When diluted to substantially lower ratios than the recommended 4:1, it will be able to clean tires, get gunk off of garage floors, and perform a number of other cleaning jobs as long as you’re very careful with it, always use gloves, and keep it away from painted plastic.

We wouldn’t choose this degreaser for extremely tough jobs; we’d use an even stronger petroleum-based product for those. But for regular engine degreasing, it’s a very good choice. And as a bonus, its citrus smell is nowhere as noxious as most other degreaser odors.


4. 3D Grand Blast Engine Degreaser

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This is our second non-toxic, biodegradable green degreaser, and it’s best used to handle lighter buildups of grease and dirt on engines. At the very least, you’ll have to add a good deal of elbow grease to remove the caked-on stuff that stronger products will eat up and spit out (figuratively speaking, of course). It’s relatively inexpensive for a one-gallon jug that can be diluted, with a recommended ratio of 4:1 for heavy engine work and 20:1 for lighter jobs like undercarriages and wheel wells, but we’d recommend using it straight out of the container to get a decent shine back on your engine.

3D Grand Blast does contain sodium hydroxide and alcohol, so while it’s not toxic it can still cause paint to fade (or hands to become irritated). Using gloves and being careful with the degreaser and its run-off would be a very good idea. On the flip side, this is one of the few degreasing solutions which can be safely used in most pressure washers. And if you’re looking for an odorless product, this one comes the closest to scent-free among all the degreasers we’ve reviewed.


5. Zep Industrial Purpose Degreaser Aerosol

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This would qualify as our bargain choice, but it works so well it almost seems disrespectful to call it that. Zep contains no petroleum-based ingredients, but does use caustic sodium hydroxide as one of its cleaning agents so the cautions we’ve mentioned for other products apply here as well, including wearing gloves and avoiding painted surfaces.

This is another concentrate which can be used in strong 5:1 solutions for engine cleaning and weaker ones to clean grease from floors, work surfaces and tools. And you’ll find it in many commercial auto and detailing shops, not only because of Zep’s sterling reputation, but because their degreaser is a very good performer. Letting it sink in for a while and then washing it off will take care of most caked-on grease and tough to remove gunk.

If you prefer a foam degreaser which is even more versatile (but has to be wiped off after application), Zep’s Heavy Duty Foaming Citrus Degreaser is another excellent product you may want to check out as well.

What to Look for Engine Dregreaser

engine degreaser featured

It would be easy to think that all engine degreasers are the same. In truth, they’re not. There are big differences between the three major types of degreasers, and making the right decision depends on your preferences and your budget.

Types of Degreasers

The ingredients in an engine degreaser can have a major impact on its strength, its cost and whether you’re able to use it for other automotive cleaning jobs. So that’s the first thing to look at when you’re shopping at online or the auto parts store.

Petroleum-Based Degreasers

These are usually the choice of professionals, because the powerful oil and petroleum distillates contained in them are able to easily loosen and then dissolve most of the grease and gunk that accumulates on an engine. They must be used with care, because they’re so abrasive that their run-off can damage (or at least remove the paint) from plastic, rubber or other parts under the hood. These degreasers are the least expensive type to purchase, and the highest performing.

Water-Based Degreasers

Without strong petroleum-based ingredients, water-based degreasers must rely on chemical formulations to do their work. That makes them milder and not quite as effective against stubborn buildups. They work well for removing most normal engine grease and oil, however, and their wash-off won’t be a problem in terms of damaging other components. These degreasers are normally more expensive and are always more environmentally-friendly.

Foam Degreasers

Foam degreasers can be somewhat difficult to use until you get used to them, because you can’t simply wash them off after they’ve been applied. The foam loosens and picks up grease, and the combination must then be carefully removed with a cloth – carefully, because that’s a potentially-messy task.

There’s a major benefit to relatively-expensive foam degreasers, however. They can be used to remove dirt and grime from just about anywhere on your car, or even on other motors and appliances, without doing any damage.

Single-Purpose vs Multi-Purpose Degreasers

We’ve touched on most of the important points already, since as you’ve probably understood by now, foam degreasers are able to be used for multiple applications, while most petroleum- and water-based ones aren’t – although concentrated solutions can often be diluted to be used on other non-painted car parts.

If you know in advance that you’ll only be degreasing your vehicle’s engine, it makes sense to choose a powerful single-purpose product. It will do the job more effectively than a degreaser which will also clean other contaminants from other types of surfaces, such as removing oil from the garage floor, gasoline spills on a lawnmower or paint from the sidewalk.

There’s a cost/benefit value to a multi-purpose degreaser; it will generally cost more, but you’ll be able to perform more tasks without buying a number of solvents to handle them.

If you do plan to use a degreasing product for more than just your engine, be sure to read the label carefully. Most will tell you the types of surfaces or equipment they’re suited for. And since there’s no “right” section to put this warning in, we’ll put it here: when degreasing your engine, be sure to cover up all electronics, the carburetor, the distributor cap and all air intakes beforehand.

Other Buying Considerations

Degreaser is sold in both concentrated and “out of the bottle” formulas. Commercial and industrial users are best served with the concentrate, which can be mixed to any strength and is more economical in the long run. Home mechanics aren’t likely to need concentrate, since they will only be degreasing their engine every once in a while.

Degreasing an engine isn’t just messy; it can also be very smelly. Many degreasing solutions have a strong odor, either because of the petroleum products and solvents in them, or the alternative mix of green ingredients which each have their own distinct aromas. Some also have added scents meant to cover noxious odors, but also create one of their own. You can find some degreasers which are odorless, and that’s a good idea if you have allergies or respiratory issues. At the very least, be sure to get a face mask and gloves if you’re going to be working with gasoline-based degreasers.

Final Thoughts

Degreasing an engine isn’t particularly enjoyable, even for dedicated grease monkeys. Using the right type of degreaser, and taking the proper precautions to be able to clean up easily afterward, will make the job much easier to take. The real enjoyment comes afterward, when you look at your sparkling engine block and realize that it really can look like that, even months or years after you bought the car.

Richard Reed
Author

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