I am planning to buy some lowering spring kit. I am noticing from measuring between the tire and body that the passenger side is about 1 inch higher than the driver side.

Do you guys think buying lowering spring kit will balance this?

bump

The problem could be in your shocks/struts

And if not the springs will not correct the difference. You'd have to either cut a spring mount or get coilovers.

How many miles are on your car?

Springs do sag as they get older

160k

Are you or has someone in the past that was REALLY large, driven the car a lot? Don't laugh, it WILL compress the springs. I knew a guy that weighed 345 pounds, he drove a 1975 Mitsubishi Station wagon for ten years. That thing drug the ground on the drivers side even when he wasn't in it.

Springs sag over time, but other things to consider is the overall condition of the suspension. Have you visually inspected the lower side? I've seen odd things happen to suspensions over time including broken coils, worn or broken bushings and balljoints.

Prior to installing aftermarket parts you may want to visually inspect your suspension for broken components