Open Clusters (OCs) are widely used as tracers of the formation and evolution of the Galaxy, as well as test cases for stellar evolution andn dynamical interaction theories. In particular, nearby OCs spanning a wide age range are commonly used as benchmark objects for galactic and stellar studies owing to the highest precision that is achievable in all their parameters. We have designed a project to perform an in-depth study of ~30 nearby (closer than 500 pc) and old (age>300Myr) OCs. After Gaia DR2, very accurate memberships, distances, ages, and motions are available for these OCs. We have used a strictly line-by-line differential analysis method with high-resolution, high signal-to-noise spectra of very certain member stars. I will present the first results of this project where we aim to measure the cluster internal dispersions of abundances at different evolutionary stages, and compare their chemical signatures. This type of study is useful to better understand a handful of processes: star formation, evolution, pollution and accretion processes, and the effect of the presence of planets. Moreover, this test case can constrain the applicability of chemical tagging in the field of Galactic archeology.