when light is on – that means the OD is off it’s like a overdrive TOWING want extra power when it’s off this means you’re in OD mode.Every day city driving but you can use your overdrive anytime you want some extra power but the light will be on in the dash to tell you it’s on and the RPMs will be slightly higher about 200 250 RPMs . When light is not on – this means regular driving mode hope this helped you out DODGEZILLA