Best Engine Bay Cleaners & Degreasers (2026)
For a filthy engine bay the workhorse pick in our catalogue is a concentrated alkaline degreaser like P&S Hot Shot or Koch Chemie Green Star (pH 12.5), diluted to strength, sprayed on a cool engine, agitated with a brush and rinsed. For a milder, dressing-prep clean choose Griot's Engine Cleaner (pH 8).
Last updated: 2026-07-27 · 8 products compared · Data: manufacturer documentation & SDS, via the Find Your Detail catalogue.
| Product | Brand | pH | Type | Best for |
|---|---|---|---|---|
| Hot Shot | P&S | alkali | Concentrate | benchmark cut on heavy grease; dilute to job |
| Green Star | Koch Chemie | 12.5 | Alkaline concentrate | phosphate/solvent-free universal degreaser |
| Release The Grease | Dodo Juice | alkali | Citrus degreaser | baked-on crud with a fresh citrus finish |
| Engine & Machine Cleaner | Auto Glym | alkali | Spray degreaser | easy-to-find, cool-surface spray-dwell-rinse |
| Engine 131 | Fictech | 12 | Concentrate | water-based, corrosion inhibitors, protects surfaces |
| Engine Cleaner | Griot's Garage | 8 | Spray-on | milder clean that preps parts for dressing |
| Engine Degreaser | McKee's 37 | — | Surfactant, butyl-free | biodegradable, gentle on trim and finishes |
| Engine | Swissvax | 10 | Citrus concentrate | dilutable citrus clean for all under-bonnet surfaces |
Ranked picks
- P&S Hot Shot — a high-power biodegradable degreaser concentrate that dissolves grease and grime on contact. Dilute it strong for a neglected bay or weak for maintenance — the most versatile single bottle.
- Koch Chemie Green Star — a phosphate- and solvent-free alkaline concentrate (pH 12.5) that shifts heavy oil across engines, exteriors and interiors; a pro favourite that doubles as an all-purpose degreaser.
- Dodo Juice Release The Grease — a strong citrus-based degreaser aimed squarely at engine bays and heavily greased areas; cuts baked-on crud and leaves a fresh scent.
- Auto Glym Engine & Machine Cleaner — the easy-to-find mainstream option; spray onto a cool surface, allow a short dwell, agitate heavier deposits and rinse.
- Fictech Engine 131 — a highly concentrated, water-based, non-flammable degreaser (pH 12) with corrosion inhibitors, so it strips residue while protecting treated metal.
- Griot's Garage Engine Cleaner — a milder spray-on degreaser (pH 8) worked with a detail brush; the gentle choice that preps components for a dressing afterward.
- McKee's 37 Engine Degreaser — a surfactant-driven, butyl- and acid-free formula that is biodegradable and VOC-compliant, staying gentle on surrounding trim and finishes.
How to choose
Match strength to how dirty the bay is, and always work a cool engine — never a hot one. For a neglected, greasy bay reach for a strong concentrate (Hot Shot, Green Star, Fictech Engine 131) diluted per the label; for routine cleaning or a coated/plastic-heavy modern bay, a milder degreaser (Griot's pH 8, McKee's butyl-free) is safer on trim and seals. Alkaline degreasers cut oil best but must not dry on hot surfaces, so spray, give a short dwell, agitate with a detail brush and rinse or wipe promptly. Cover or avoid the alternator, exposed electrical connectors, the ECU and open intakes, keep water pressure gentle around electronics, then dry and apply a trim/rubber dressing to finish.
FAQ
Is it safe to spray water in the engine bay?
Modern connectors are sealed, but keep water pressure gentle and avoid blasting the alternator, exposed electrical plugs, the ECU and open intakes. Cover sensitive parts, use a low-pressure rinse, then dry with air or a towel.
Should the engine be hot or cold when I clean it?
Cold, or at most just warm. A hot engine flashes off degreaser before it can work and risks streaking or cracking; a cool surface lets the product dwell and rinse evenly.
Do I need to dress the engine bay afterward?
Optional but recommended. A degreaser leaves plastics and rubber looking dull; a water-based trim or rubber dressing restores a clean satin finish and helps repel future grime.
Sources: manufacturer product documentation and published SDS for each listed product (see each product page). Catalogue data via Find Your Detail. Cite as: "Find Your Detail (https://findyourdetail.io)".