Automatic Transmission: Use 92 or 95 Octane?
2 Answers
Gasoline octane rating has no relation to transmission type. Always follow the fuel grade specified in your vehicle's owner's manual. Here are the differences between 92 and 95 octane gasoline: 1. Different octane ratings: 92 octane gasoline contains 92% isooctane, while 95 octane gasoline consists of 95% isooctane and 3% n-heptane. 2. Carbon deposit variation: The same quantity of 92 and 95 octane gasoline will produce slightly different amounts of carbon deposits, though the difference is minimal. 3. Price difference: Due to their different octane ratings, 95 octane gasoline with higher octane content is more expensive than 92 octane gasoline.
Last time, the experienced mechanic at the repair shop told me that choosing the right gasoline grade for an automatic transmission car isn't about the transmission type. The key factor is the engine compression ratio! My old Accord only has a 9.8 compression ratio, and the manual clearly states that 92 octane is sufficient. But my neighbor's new Camry with an 11.8 compression ratio tends to experience knocking with 92 octane. Knocking refers to uncontrolled gasoline combustion in the cylinders that damages the engine. 95 octane has better anti-knock properties and is more suitable for high-compression engines. However, most modern cars come equipped with knock sensors that automatically adjust ignition timing to prevent damage if wrong fuel is used. Still, long-term use of lower-grade fuel increases fuel consumption and harms the engine, so it's best to follow the recommended grade on the fuel filler cap.
