Many, many, many people get in trouble for volunteering information they don't need to to the cops. Don't volunteer anything. Never lie, but then, never, EVER, volunteer for a police search of your vehicle, even if you [think you] have nothing to hide. Cops will oftentimes ASK to search your vehicle. Don't let them. Even if you're honest and they're honest, nothing good will come of it. Be polite, and if they're determined to search your car anyway, tell them to go ahead, but note that it is without your consent.
Never give an affirmation. That can be taken the wrong way.
People will always be people, and hear what they want.