What is a good homemade engine cleaner?

[VanCassidy]

A highly effective homemade engine cleaner can be made for under $5 using common household ingredients like dish soap and isopropyl alcohol. This mixture safely cuts through most grease and grime without damaging engine components. For heavily soiled areas, a paste of baking soda and water provides gentle abrasive action. These solutions offer a cost-effective, non-toxic alternative to many commercial degreasers, with a typical cleaning session costing less than a commercial can.

The key is understanding the chemistry. Grease and oil are non-polar substances, so they resist water. Effective cleaners use surfactants (like those in dish soap) to break surface tension and emulsify grease, or solvents (like alcohol) to dissolve it. A simple yet powerful blend is one part Dawn Ultra Dish Soap, one part 70% isopropyl alcohol, and two parts water. Shake well in a spray bottle. The soap lifts the grease, and the alcohol helps it evaporate quickly, preventing water from pooling in electrical components.

For different soil levels, adjust the formula. A comparison of effective recipes is below:

Cleaner Type	Best For	Ingredients & Ratio	Key Action	Cost per Use
All-Purpose Degreaser	General grease, light oil	Dawn Ultra (1), 70% IPA (1), Water (2)	Emulsifies & dissolves	~$0.50
Heavy-Duty Paste	Caked-on grime, carbon deposits	Baking Soda, Water (to paste)	Mild abrasive scrubbing	~$0.10
Rinse-Free Wipe	Quick touch-ups, sensitive areas	Undiluted 70% Isopropyl Alcohol	Dissolves & evaporates	~$0.25

Apply the all-purpose spray to a cool engine, agitate with a soft brush, and let it sit for 3-5 minutes. Avoid direct spraying on alternators, fuse boxes, or open air intakes. Wipe or rinse with low-pressure water. The baking soda paste can be scrubbed onto stubborn spots with a toothbrush, then rinsed. Industry practice notes that regular mild cleaning with these solutions can prevent corrosive buildup, potentially extending component life. Always work in a well-ventilated area and wear gloves. While excellent for maintenance, these are not substitutes for professional solvent-based cleaning for severe, decades-old engine sludge.

[DeHadley]

I’ve been using my own mix for years on my classic car. My go-to is simple: blue Dawn and rubbing alcohol. I keep it in a labeled spray bottle in the garage. For the really tough stuff, like the grease built up on the valve cover, I make a thick paste with baking soda. It bubbles a bit and then the grime wipes right off. The best part? I know exactly what’s going onto my engine—no harsh chemical smells. It’s cheap, it works, and I can clean the engine anytime without a special trip to the store.

[LaIris]

Let’s talk safety and results. As a weekend mechanic, my primary concern is not harming the engine. A cool engine is non-negotiable. I avoid high-pressure water. My process: spray the soap-alcohol mix, wait a few minutes, then gently agitate. The grease literally melts away. For electrical parts, I use a cloth dampened with just the alcohol—it cleans and dries fast. I tried the vinegar-based recipes you see online; they’re not effective for automotive grease. Stick with detergent-based solutions. The dollar-store brush and your homemade cleaner will make the bay look 80% better with almost zero risk.

[McSimon]

Looking at this from a pure cost and logistics angle, homemade wins. A gallon of name-brand engine degreaser costs about $15. I can make a half-gallon of my effective cleaner for about $2 using soap I already have and a bottle of alcohol. That’s a massive saving per use. It’s also more convenient. I ran out once before a car show, and in five minutes, I had a fresh batch mixed. No waiting for store runs. For the average person doing one or two cleanings a year, the commercial can might seem easier, but it’s often overkill and more expensive for the same visual result.

[StAdriana]

My perspective is environmental. Commercial aerosol degreasers often contain volatile organic compounds and synthetic chemicals. When I wash my car, that runoff goes somewhere. My homemade cleaner uses biodegradable dish soap and alcohol that breaks down more easily. I use less plastic because I refill my spray bottle from bulk ingredients. It’s a small step, but it matters. Performance-wise, it cleans just as well for routine maintenance. For the heavy-duty, caked-on oil sludge from a neglected engine, yes, you might need a stronger, professional product. But for 90% of us just keeping our daily driver’s engine bay tidy, the homemade option is effective, responsible, and puts you in control of what you use.