With rates on rental cars down because of the economy, many renters are using them to do messy jobs that they don't want to use their own vehicles for. The result can be an unwanted odor problem that rental car companies are striving to fix in an effort to keep their customers happy. Among the weapons in the aroma wars are air fresheners and, in some extreme cases, steam-cleaners. Smoke smells, however, are still the number 1 customer complaint. To combat the problem, some companies have designated portions of their fleets nonsmoking, posting no-smoking signs and removing ashtrays. Give any rental car a smell test before you drive it off the lot. If it fails, ask the agent to give you a different car.