If your favorite gas station or supplier decides to save a few cents by adding less dispersant-detergent additives to its fuel or skipping it altogether then your injectors will eventually become clogged with varnish deposits. These deposits disrupt proper fuel atomization and mixing, creating a lean fuel mixture that leads to misfiring and driveability problems. The injectors in the middle cylinders, where temperatures are highest, generally clog most quickly. The solution? Clean your fuel injectors, then switch to a higher quality supplier.