It’s more efficient to shut off your engine and restart it any time you stop for more than a few seconds. Even Ford has finally figured that out:
In a move to boost fuel economy, Ford Motor Co. said Monday it will add an Auto Start-Stop system that shuts off the engine when a vehicle comes to a stop. The automaker said the feature will be added to its conventional cars, crossovers and SUVs in North America.
Ford’s statement said that the feature is expected to boost fuel economy by between 4% and 10%, and eliminate tailpipe emissions while the vehicle is stationary.
Better to stop using the drive-through.