Using your neighbor's grill without their permission, even if you clean it afterward, could be considered rude and disrespectful of their property. Borrowing someone else's belongings, especially something as personal as a grill, without explicit consent is not appropriate.
Instead, if you want to use your neighbor's grill for your party, it's essential to ask for their permission first. Approach them in a friendly manner and explain your situation. If they are comfortable with the idea, they might allow you to use it. Be sure to clarify any specific conditions they may have, such as how they want it returned or if they expect you to provide your own grilling supplies.
Respecting your neighbor's property and boundaries is crucial for maintaining a positive relationship with them. So always seek permission before using someone else's belongings, and if they decline, it's essential to accept their decision graciously. If borrowing a grill isn't possible, consider using your own or renting one for your party.