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Regular Unleaded Gasoline
The recommended gasoline for most cars is regular 87 octane. One common misconception is that higher octane gasoline contains more cleaning additives than lower octane gas. All octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against engine deposit build-up. In fact, using a gasoline with too high of an octane rating may cause damage to the emissions system.
• Gasoline and Octane Ratings - This article defines octane ratings and provides an overview of how gasoline in made.
Mid-Grade Gasoline
The octane ratings 'regular', 'mid-grade', and 'premium' are not consistent. In the United States, for example, one state may require a minimum octane rating of 92 for premium gasoline, while another may allow an octane rating of 90 to be premium. Check the octane rating on the yellow sticker on the gas pump rather than relying on descriptive labels.
Premium Gasoline
Certain high performance engines benefit from use of high octane fuel. For other engines, using a fuel with a higher octane rating than the vehicle requires sends unburned fuel into the emissions system and catalytic converter. This puts unecessary stress on the emissions system. For some vehicles, a rotten egg smell coming from the tailpipe signals use of too-high octane gas.
Leaded Gasoline
Many countries continue to use leaded gasoline, even though lead exposure has significant health and environmental consequences and the cost of switching to unleaded gasoline is relatively low. Although greatly improved, research indicates significant health and environmental effects from use of leaded gasoline remain even in countries that have switched to unleaded fuel.
Synthetic and Reformulated Fuels
Some major cities with air pollution problems require the use of reformulated gasoline. Reformulated gasoline is an oxygenated fuel that burns cleanly but can lower fuel economy and engine performance slightly. Reformulated gasoline may cause pinging or premature burn in engines with excessive carbon deposits. Older/dirtier engines may benefit from stepping up to the next grade of gasoline.
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