In some cases coasting in neutral will save fuel, in others it will not. This depends on the specific situation. If you're coasting down a hill to a stop, then

In some cases coasting in neutral will save fuel, in others it will not. This depends on the specific situation. If you're coasting down a hill to a stop, then it's better to coast in gear to use approximately no fuel. If you're coasting down a hill to long level stretch of road it's better to coast in neutral to obtain kinetic energy. If one wants to follow speed limits it's sometimes necessary to first coast in neutral then use engine braking at the bottom of the hill. The optimal strategy in all cases is actually coasting in neutral with the engine turned off, and then starting the engine when you need to increase your speed. (This advanced technique may be illegal, though).