Final answer:
The best substance for cleaning cylinder walls after boring or honing is a soap and water solution, as it effectively removes debris without leaving harmful residues.
Step-by-step explanation:
After performing cylinder work such as boring or honing, it is important to thoroughly clean the cylinder walls to remove any debris, metal filings, or honing residue that could cause damage to the engine during operation. The best substance to use for cleaning the cylinder walls is a soap and water solution. Fresh engine oil, while important as a lubricant and protectant after cleaning, is not ideal for cleaning purposes. Solvents could potentially leave a residue, affecting the oil's lubrication properties, and gasoline is dangerous due to its flammability and is not a recommended cleaning agent due to potential health hazards.