TOP TIER is a standard of gasoline that contains higher levels of detergent additives than current Canadian Government Standards Board (CGSB) standards. The CGSB requires that all gasoline marketed in Canada contain detergents, which are added to gasoline to help clean fuel injectors, intake valves and other engine parts.* The TOP TIER standard is set by a governing body of several automakers and is recommended in their vehicles’ owner manuals. Esso gasoline contains significantly more detergents than the minimum quantity required by the CGSB and has passed other performance tests, such as deposit control on intake valves and fuel injectors, resulting in it being certified TOP TIER. Not only does our gasoline help keep vital engine parts clean, we also remove deposits as you drive.