Anyone use fuel system cleaners?

I've used the Lucas cleaner I buy at Walmart in 32oz (I think) bottles in my Dakota and small engines (lawn mower, generator, etc.) I know it works because I've had issues starting my lawn mower after it sat for a long time. After just adding the Lucas and letting it sit for a few days, it started right up! Used regularly in my generator and it starts right up after sitting for months.