Poke your head under the bonnet of your car and chances are you'll find a thin layer of grease, oil and muck coating just about everything. Not only does this make your car look like it's been trapped in the boiler room of a ship, but it can also mask serious problems until it's too late.
Small cracks and leaks, perished gaskets and even rust can be hidden under this gunk, which makes it a good idea to keep your engine bay clean so you can spot these issues before they become serious money pits.
Degreaser is the best way to clean an engine. It uses hydrophobic and hydrophilic molecules to help dislodge oil and allow you to simply wash the oil off. We've chosen our favourite examples, looking at price, environmental impact and effectiveness so you know which one is perfect for you.
The best degreaser
Bilt Hamber Surfex HD Cleaner
The best degreaser and APC
Combining degreaser and all-purpose cleaner (APC), Bilt Hamber Surfex HD Cleaner is our current favourite degreaser. Fully biodegradable and water-based, it's an effective choice for removing stubborn grease, organic deposits and oil without damaging the planet. Available as either a one-litre spray or a five-litre bottle, it can be diluted to clean paintwork, carpets, wheels and tyres. It's also great value for money and top quality too.
Autoglym Engine & Machine Cleaner
The best degreaser and detergent
Another top choice for degreaser, this water-based degreaser is an eco-friendly way of dislodging oil, grease, grime and traffic film. As well as working as a degreaser, it also features a detergent element to help clean surfaces as well as removing grime. If the bottle was a bit bigger and a tiny bit cheaper it'd probably nab the top spot.
STP GST73500ENP Engine Degreaser Professional Series 500 ml
The best degreaser for really mucky surfaces
Perfect if your engine is saturated in more oil than a dodgy kebab, this heavy-duty engine degreaser is designed to penetrate and dissolve oil and other tough deposits. It's a bit overkill for most applications and being petroleum-based it can damage rubber, asphalt and paintwork but nothing is as good on tough grease as this.
Granville Gunk 734 5L Degreaser
The best bulk degreaser
This big metal tin of degreaser is probably something you'd find in your grandad's shed but it's a decent choice for larger jobs, like dismantling and restoring an engine. Designed to be brushed on, it's solvent-based and good for grime, even if it does leave an annoying white film.
Meguiar's G180224EU Heavy Duty Multi-Purpose Cleaner
The best degreaser for general use
Nowhere near as good as the other degreasers on oil and grease, this option from Meguiar's is a fantastic multi-purpose cleaner that can be used on grease in a pinch. What's impressive about this is that it can be sprayed onto metal, rubber, plastics and fabrics and clean without needing to be diluted like the Bilt Hamber option. Still, it's not a particularly good degreaser that needs to be remembered when shopping.
The best brushes for your engine bay
What you need to know about degreaser
Is degreaser dangerous?
Yes, degreasers aren't something you particularly want to ingest. Most of them will cause eye and skin irritation, while the solvent-based ones are flammable and can cause drowsiness or dizziness.
Old kerosene-based degreasers are particularly nasty to pretty much anything living, and as water-based options are far better at removing grease, there's no real need to rely on solvent-based options anymore.
Water-based options are often biodegradable which means you won't be damaging the planet while you clean your engine bay.
Why should I keep my engine bay clean?
A clean engine bay may seem a little unnecessary considering you hopefully don't spend a lot of time under your bonnet, but it makes a lot of sense to keep it clean. Not only will a clean engine bay help when it comes to sale time, but a clean engine bay will make catching any mechanical issues easier to spot before they become serious.
How do I clean my engine?
- Run your engine for a couple of minutes (five should do) and then turn your engine off. This will heat the deposits and make removing them easier.
- Lift the bonnet and make sure the engine bay is cool enough that you won't roast your fingers as you clean the engine.
- Remove the engine cover if there is one and put it to the side. You can clean that separately.
- Prepare the engine bay for cleaning by covering the sensitive electric bits in plastic bags. Make sure to cover the battery (disconnect the negative terminal too), ignition wires and ECU. Also cover the air filter to keep everything safe.
- Apply the degreaser to the engine bay, being liberal with how much you add. You can add some to your engine cover too.
- Allow a couple of minutes for the degreaser to penetrate the grease and then scrub it with an appropriate brush to make sure you've loosened the grease.
- Wash it down with a hose and remove any existing water with a drying towel.
- When the engine is dried, remove the plastic bags and reattach the engine cover.