Top Tier gasoline contains more effective detergents than federally required, which helps clean fuel injectors and reduce harmful carbon deposits inside the engine.

Oil companies and gas-station chains love to boast about their fuels, how they burn the cleanest or deliver the most ...

Gasoline producers can use more detergent in a blend than is required by Top Tier, though, and that's what Shell has done with its V-Power premium; it contains the highest detergent concentration.