Top 10 check-engine-light car repairs
No. 2 car repair: Loose fuel cap
Average repair cost: 10 cents
A gas cap that is missing or damaged can trigger a check-engine light and result in a small -- 0.5 percent -- drop in gas mileage. In the study, it accounted for 7.21 percent of repairs, down from 9.28 percent two years ago.
CarMD noted that the low cost means most mechanics are diagnosing this problem at no charge to their customers. Expect to spend a couple of dollars if the gas cap needs replacing versus just tightening.