How to detail an engine bay safely

Engine bays collect a mix of oil mist, road dust and winter grit. Cleaning one is not dangerous if you respect three things: the engine must be cold, sensitive electrics must be protected, and water should be a gentle rinse, not a blast. If your car is a hybrid or electric vehicle, or you are not sure what something is, leave it to a professional.

1. 1

   Start stone cold

   Work only on an engine that has been off for at least an hour, ideally first thing in the morning. Cold water on a hot block or turbo is a risk, and cleaner evaporates on hot metal.

2. 2

   Cover the sensitive parts

   Bag and tape the alternator, the exposed air intake, the fuse box and any open connectors. Disconnecting the battery is optional on modern cars — check your manual.

3. 3

   Spray and agitate

   Mist APC Pro at 1:10 on plastics, hoses and painted surfaces, and 1:5 on greasy spots. Agitate with soft brushes and give it a minute or two to work. Do not let it dry.

4. 4

   Rinse gently

   A light mist from a hose, or a pressure washer on the widest fan from well back. Never aim directly at connectors, the fuse box or sensors. Many detailers skip the rinse entirely and wipe with damp microfibres instead.

5. 5

   Dry and idle

   Blow or towel off standing water, remove the bags, and let the engine idle for ten minutes with the bonnet open to dry everything out.

   Bay tip · Wipe the underside of the bonnet and the scuttle panel with the same mix — leaves and dust collect there in winter.

Safety: Gloves and eye protection on. Engine off, key out, cold engine. Keep cleaner off belts and away from hot exhaust parts. If in doubt, book a professional rather than guessing.