One easy way to save money on gas while doing lawn care is to ease up on the throttle of your weed trimmer. Unless you are trimming an overgrown ditch , there is no need to run a weed eater wide open. About half throttle is plenty on normal trimming. For example, in my lawn care business where we may mow 9 yards a day we never use a full gallon of mixed gas for our weed trimmers.
